That contest i hardly solved 3 problem..and CF Predictor said i will be specialist..there had 12-hours hack phase..So i did not sleep well at night :( after every some times i wake up and checked any problem hacked or not.. But when no hack with no system failed i saw my profile specialist tag..that's a clearly my happiest moment in CF of my previous 7 months hard work :D

/*
ID: varunra2
LANG: C++
TASK: grass
*/
 
#include <bits/stdc++.h>
using namespace std;
 
#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif
 
#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second
 
const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;
 
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
 
// https://codeforces.net/blog/entry/50889?#comment-348725
// credits to that comment for this geniosity approach
 
// so wtf are we doing
// we have a lazy seg tree
// for each node, all its children form a subarray
// and group together similar types
// ofc you should allocate extra memory to move nodes around
// then it is just a simple range min query of the entire segtree
 
// so how to reorder
// we need extra spaces
// without spaces it is easy to do
// simple dfs
// then whenever you get called append all of your children
// after you are done appending
// call dfs on each of your children
// thats it
// now for updates...
// whenver you change color of node u from A -> B
// increase the of where node u is now by INF
// then it increases all children of node u with color A by INF
// then it decreases all children of node u with color B by INF
// then wherever u needs to go decrease by INF i think lmao
// oh god its a nightmare to implement
 
// things to take care of during update
// increase value of current node by INF
// decrease value of new position by INF
// increase all old children of u with same color by INF
// decrease all children of u with new color by INF
// print global min of segtree
 
int n, m, k, q;
vector<VII> adj;
vector<pair<int, PII>> edg;
vector<VII> mst;
VI par;               // for dsu/mst
VI siz;               // for dsu/mst
VI from;              // your parent, but "par" is taken
VI curcol;            // what is each nodes current color
vector<MPII> colcnt;  // how many of each color does each node have at max note:
                      // this never goes down lmao
MPII cnt0;            // for the root node, cuz he doesn't have a parent.
vector<map<int, PII>> sten;  // crucial for ordering
map<int, PII> sten0;
// holds the start and end points of every color for each parent node
vector<ll> lazy;
vector<ll> st;
vector<ll> wt;         // weight of each node
vector<MPII> curfreq;  // holds frequency count for each color for all children
                       // of some node
MPII curfreq0;
// note: this count never goes down
// even if a node switches from color a -> b, the only thing that changes is
// that parent's frequency count for b, which increases by 1, while their count
// for "a" remains the same
int lzysiz = 0;
int N;
 
VI curind;  // index of each node in the segtree
VII qrys;
 
void print_segtree(vector<ll>& segtree, string s = "") {
  int siz = (int)segtree.size();
  // 0
  // 1, 2
  // 3, 4, 5, 6
  // 7, 8, 9, 10, 11, 12, 13, 14...
  cout << "Printing seg tree " << s << endl;
  for (int i = 0; i < siz; i++) {
    cout << segtree[i] << " ";
    if (__builtin_popcount(i + 2) == 1) cout << endl;
  }
  cout << endl;
}
 
void init() {
  adj.resize(n);
  from.resize(n);
  mst.resize(n);
  par.resize(n);
  siz.resize(n);
  curcol.resize(n);
  colcnt.resize(n);
  sten.resize(n);
  curind.resize(n);
  curfreq.resize(n);
  wt.resize(n);
  wt[0] = INF;
 
  edg.resize(m);
 
  qrys.resize(q);
 
  for (int i = 0; i < n; i++) {
    par[i] = i;
    siz[i] = 1;
  }
}
 
// dsu ds
// just for mst
 
int find(int x) {
  while (par[x] != par[par[x]]) par[x] = par[par[x]];
  return par[x];
}
 
bool same(int x, int y) { return find(x) == find(y); }
 
void merge(int x, int y) {
  x = find(x);
  y = find(y);
  if (siz[x] < siz[y]) swap(x, y);
  siz[x] += y;
  par[y] = x;
}
 
void dfs_par(int u, int v) {
  // dfs to get your parents
  // keep that info on from
  from[u] = v;
  for (auto& x : mst[u]) {
    if (x.x == v) continue;
    wt[x.x] = x.y;
    dfs_par(x.x, u);
  }
}
 
int cur_ind = 0;
 
void dfs_ord(int u, int v) {
  if (!u) {
    for (auto& x : cnt0) {
      sten0[x.x].x = cur_ind;
      sten0[x.x].y = cur_ind + x.y - 1;
      cur_ind += x.y;
    }
  }
  for (auto& x : colcnt[u]) {
    sten[u][x.x].x = cur_ind;
    sten[u][x.x].y = cur_ind + x.y - 1;  // bounds are inclusive
    cur_ind += x.y;
  }
  // now we can do dfs
  for (auto& x : mst[u]) {
    if (x.x == v) continue;
    dfs_ord(x.x, u);
  }
}
 
// too lazy to post link
// ekzlib something something
 
void push(int lo, int hi, int node) {
  if (lazy[node] == 0) return;
  st[node] += lazy[node];
  if (lo != hi) {
    lazy[2 * node + 1] += lazy[node];
    lazy[2 * node + 2] += lazy[node];
  }
  lazy[node] = 0;
}
 
void update_range(int s, int e, ll x, int lo = 0, int hi = -1, int node = 0) {
  if (hi == -1) hi = N - 1;
  push(lo, hi, node);
  if (hi < s || lo > e) return;
  if (lo >= s && hi <= e) {
    lazy[node] = x;
    push(lo, hi, node);
    return;
  }
  int mid = (lo + hi) / 2;
  update_range(s, e, x, lo, mid, 2 * node + 1);
  update_range(s, e, x, mid + 1, hi, 2 * node + 2);
  st[node] = min(st[2 * node + 1], st[2 * node + 2]);
}
 
ll query(int s, int e, int lo = 0, int hi = -1, int node = 0) {
  if (hi == -1) hi = N - 1;
  push(lo, hi, node);
  if (hi < s || lo > e) return 0;
  if (lo >= s && hi <= e) return st[node];
  int mid = (lo + hi) / 2;
  return min(query(s, e, lo, mid, 2 * node + 1),
             query(s, e, mid + 1, hi, 2 * node + 2));
}
 
void make_ordering() {
  // in this section of the code we need to make the ordering
  // things to fill out
  //  sten
  //  lzy
  // st
  lzysiz = n + q + 1;
  N = lzysiz;
  lzysiz *= 4;
  lazy.resize(lzysiz);  // whoops forgot about the actual st
  st.resize(lzysiz);
  // we need to make everybody become INF
  // for (int i = 0; i < lzysiz; i++) {
  //   lazy[i] = INF;
  //   st[i] = 0;
  // }
  // swap(st, lazy);
 
  for (int i = 0; i < N; i++) {
    update_range(i, i, INF);
  }
 
  dfs_ord(0, -1);
  // sten is filled out
}
 
void init_segtree() {
  // we need to fill out the segment tree
  // originally everything is at INF
  // things to modify/update
  //  curind
  //  st
  for (int i = 0; i < n; i++) {
    curind[i] = -1;
  }
 
  // so we have to determine everybody's indices
  // all indices that are actually there are and same color as parent will just
  // have edge weight all indices that are actually there but not the same color
  // as parent will have edge weight + INF all indices that are not there but if
  // they were they would have same weight as parent will have edge weight + INF
  // all indices that are not there and have different weight than parent will
  // have weight = 2 * INF
  //^^^^^^^^^^^^^ for weights only
  // we still have to figure out indices
 
  // first we should determine the weight for node 0
  // if we can figure this out, it should be easily extendable.. right?
  // oh yeah
  // get their current color
  // and then index that lmao
  curind[0] = sten0[curcol[0]].x +
              curfreq0[curcol[0]];  // obv the second part will be equal to 0
                                    // cuz i haven't changed it at all lmao
  curfreq0[curcol[0]]++;
 
  for (int i = 1; i < n; i++) {
    // we are determining i's index now
    // how would we do that?
    curind[i] = sten[from[i]][curcol[i]].x + curfreq[from[i]][curcol[i]];
    curfreq[from[i]][curcol[i]]++;
  }
 
  // letszz go!!! reee111!!111!1
 
  // we got all the segtree indices, and it shouldn't be hard to extend it to
  // when we finally do the queries
 
  // now we need to actually update the segtree
  // debug(curind);
  // debug(sten0);
  // debug(from);
  // // debug(sten);
  // for (int i = 0; i < (int)sten.size(); i++) {
  //   debug(i, sten[i]);
  // }
  // debug(lzysiz / 4);
  // debug(st);
  // debug(lazy);
 
  // it actually works letz fckin go!! reeee
 
  // alright now for the segment tree
  // god fucking finally
 
  // wait why the fuck did i include node 0 in my segment tree
  // bruh
 
  for (int i = 0; i < n; i++) {
    // so first we should subtract INF from this node
    // wt holds the costs so that is important
    // prolly gonna use that now lmao
    int indupd;
    // first we need to figure out what index this node is at to update
    // lmao this is just curind
    indupd = curind[i];
    update_range(indupd, indupd, wt[i] - INF);  // lmao retard
    // we are subtracting INF cuz we are using that node right now
  }
 
  // now we need to subtract INF from all nodes that share the same color as us
  // rn and are our children
 
  // okay we need to manually make sure we never touch node 0
 
  int endind = 0;
  for (auto& x : sten0) {
    endind = max(endind, x.y.y);
  }
 
  update_range(0, endind, (ll)1e12);  // yup that should do it lmao
  // i shouldn't hanve to do this in the first place
  // but just to be sure lmao
 
  for (int i = 0; i < n; i++) {
    // in this loop we are going to be adding INF to all of our children with
    // the same color <<<<<<<<<<< LOOOOK HERE !!!!!!!! okay if you reached this
    // reeeeeeeeeeeeeee point then this last statement is contradictory i made a
    // mistake before we do want to add INF to nodes of same color and connected
    // to you why? cuz those edges can't contribute to the final answer
    if (colcnt[i][curcol[i]] != 0) {
      int lupd, rupd;
      lupd = sten[i][curcol[i]].x;
      rupd = sten[i][curcol[i]].y;
      update_range(lupd, rupd, INF);
    }
  }
 
  // finally we are done with segtree operations
 
  // now we can answer queries/ do updates yay!
}
 
void init_qrys() {
  make_ordering();
  init_segtree();
}
 
// imma bet 50 bucks
// everything is gonna be all butterflies and sunshine and rainbows on the
// sample input but when i submit the verdicts will be AC WA WA WA WA WA WA WA
// WA WA
 
int main() {
#ifndef ONLINE_JUDGE
  freopen("grass.in", "r", stdin);
  freopen("grass.out", "w", stdout);
#endif
  cin.sync_with_stdio(0);
  cin.tie(0);
 
  cin >> n >> m >> k >> q;
 
  init();
 
  for (int i = 0; i < m; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    u--;
    v--;
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
    edg[i] = (MP(w, MP(u, v)));
  }
 
 
 
  // cout << "i read the input\n";
 
  for (int i = 0; i < n; i++) {
    cin >> curcol[i];
  }
 
  sort(all(edg));
 
  int cnt = 0;
 
  // for (int i = 0; i < n; i++) {
  //   debug(find(i));
  // }
 
  for (int i = 0; i < m and cnt < n - 1; i++) {
    auto cur = edg[i];
    int u, v, w;
    u = cur.y.x;
    v = cur.y.y;
    w = cur.x;
    // debug(find(u));
    // debug(find(v));
    // debug(v, w);
    // debug(u, v);
    if (!same(u, v)) {
      // debug("here");
      cnt++;
      merge(u, v);
      mst[u].PB(MP(v, w));
      mst[v].PB(MP(u, w));
    }
  }
  // debug(edg);
  // debug(adj);
 
  // debug(mst);
 
  // we now have the mst
  // now we need to create the ordering
  // sed lyfe :( :( :(
  // i think first we need to read the queries
  // and then order based on that
 
  dfs_par(0, -1);
  // we now have everybody's parents
  cnt0[--curcol[0]]++;
  for (int i = 1; i < n; i++) {
    colcnt[from[i]][--curcol[i]]++;
  }
 
  for (int i = 0; i < q; i++) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    qrys[i] = MP(a, b);
    if (a) {
      colcnt[from[a]][b]++;
    } else {
      cnt0[b]++;
    }
  }
 
  // okay we have the information we need to make the ordering i think
  init_qrys();  // this is prep work for the queries
 
  for (int i = 0; i < q; i++) {
    // alright ill fill this in later lmao
    int cur_node, n_color;
    cur_node = qrys[i].x;
    n_color = qrys[i].y;
    // using long variable names cuz im too dumbosity to remember what to do
 
    // what do we have to do now
    // we have to increase current index of cur_node by INF (done)
    // decrease the value at the new index by INF (done)
    // decrease all of your children that are the same color by INF
    // increase all of your new children that are the same color by INF
    // the print the answer to global min of segtree
 
    int c_ind = curind[cur_node];
    int c_col = curcol[cur_node];
 
    update_range(c_ind, c_ind, INF);
    // now we need to determine new index
 
    int n_ind;
    if (cur_node == 0) {
      n_ind = curfreq0[n_color] + sten0[n_color].x;
      curfreq0[n_color]++;
    } else {
      n_ind =
          curfreq[from[cur_node]][n_color] + sten[from[cur_node]][n_color].x;
      curfreq[from[cur_node]][n_color]++;
    }
    curind[cur_node] = n_ind;
    curcol[cur_node] = n_color;
    update_range(
        n_ind, n_ind,
        wt[cur_node] -
            INF);  // cuz we started using it 'n shit thats why the -INF
 
    int lupd, rupd;
 
    if (colcnt[cur_node][c_col] > 0) {
      lupd = sten[cur_node][c_col].x;
      rupd = sten[cur_node][c_col].y;
      update_range(lupd, rupd, -INF);
    }
 
    if (colcnt[cur_node][n_color] > 0) {
      lupd = sten[cur_node][n_color].x;
      rupd = sten[cur_node][n_color].y;
      update_range(lupd, rupd, INF);
    }
    int ret = query(0, N - 1);
    cout << ret << endl;
 
    // time to spend another day debugging kekw
  }
 
  // print_segtree(st);
  // print_segtree(lazy, "lazy");
 
  return 0;
}

/*
ID: varunra2
LANG: C++
TASK: grass
*/
 
// broo
// ac :))))))))
// letz go!!!
// i can now rip
 
#include <bits/stdc++.h>
using namespace std;
 
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
 
// using ordered_set_less = tree<int, null_type, less<int>, rb_tree_tag,
//                               tree_order_statistics_node_update>;
// using ordered_set_equal = tree<int, null_type, less_equal<int>, rb_tree_tag,
//                                tree_order_statistics_node_update>;
// using ordered_map =
//     tree<int, int, less<int>, rb_tree_tag,
//     tree_order_statistics_node_update>;
const int RANDOM =
    chrono::high_resolution_clock::now().time_since_epoch().count();
struct chash {
  int operator()(int x) const { return x ^ RANDOM; }
};
// gp_hash_table<int, int, chash> table;
 
#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif
 
#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e7
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second
#define map unordered_map
 
const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
// typedef unordered_map<int, int> MPII;
typedef gp_hash_table<int, int, chash> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;
 
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
 
int n, m, k, q;
vector<VII> adj;
vector<pair<int, PII>> edg;
vector<VII> mst;
VI par;               // for dsu/mst
VI siz;               // for dsu/mst
VI from;              // your parent, but "par" is taken
VI curcol;            // what is each nodes current color
vector<MPII> colcnt;  // how many of each color does each node have at max note:
                      // this never goes down lmao
MPII cnt0;            // for the root node, cuz he doesn't have a parent.
vector<gp_hash_table<int, PII, chash>> sten;  // crucial for ordering
gp_hash_table<int, PII, chash> sten0;
// holds the start and end points of every color for each parent node
vector<int> lazy;
vector<int> st;
vector<int> wt;        // weight of each node
vector<MPII> curfreq;  // holds frequency count for each color for all children
                       // of some node
MPII curfreq0;
// note: this count never goes down
// even if a node switches from color a -> b, the only thing that changes is
// that parent's frequency count for b, which increases by 1, while their count
// for "a" remains the same
int lzysiz = 0;
int N;
 
VI curind;  // index of each node in the segtree
VII qrys;
 
void init() {
  adj.resize(n);
  from.resize(n);
  mst.resize(n);
  par.resize(n);
  siz.resize(n);
  curcol.resize(n);
  colcnt.resize(n);
  sten.resize(n);
  curind.resize(n);
  curfreq.resize(n);
  wt.resize(n);
  wt[0] = INF;
 
  edg.resize(m);
 
  qrys.resize(q);
 
  for (int i = 0; i < n; i++) {
    par[i] = i;
    siz[i] = 1;
  }
}
 
int find(int x) {
  while (par[x] != par[par[x]]) par[x] = par[par[x]];
  return par[x];
}
 
bool same(int x, int y) { return find(x) == find(y); }
 
void merge(int x, int y) {
  x = find(x);
  y = find(y);
  if (siz[x] < siz[y]) swap(x, y);
  siz[x] += y;
  par[y] = x;
}
 
void dfs_par(int u, int v) {
  from[u] = v;
  for (auto& x : mst[u]) {
    if (x.x == v) continue;
    wt[x.x] = x.y;
    dfs_par(x.x, u);
  }
}
 
int cur_ind = 0;
 
void dfs_ord(int u, int v) {
  if (!u) {
    for (auto& x : cnt0) {
      sten0[x.x].x = cur_ind;
      sten0[x.x].y = cur_ind + x.y - 1;
      cur_ind += x.y;
    }
  }
  for (auto& x : colcnt[u]) {
    sten[u][x.x].x = cur_ind;
    sten[u][x.x].y = cur_ind + x.y - 1;
    cur_ind += x.y;
  }
  for (auto& x : mst[u]) {
    if (x.x == v) continue;
    dfs_ord(x.x, u);
  }
}
 
void push(int lo, int hi, int node) {
  if (lazy[node] == 0) return;
  st[node] += lazy[node];
  if (lo != hi) {
    lazy[2 * node + 1] += lazy[node];
    lazy[2 * node + 2] += lazy[node];
  }
  lazy[node] = 0;
}
 
void update_range(int s, int e, int x, int lo = 0, int hi = -1, int node = 0) {
  if (hi == -1) hi = N - 1;
  push(lo, hi, node);
  if (hi < s || lo > e) return;
  if (lo >= s && hi <= e) {
    lazy[node] = x;
    push(lo, hi, node);
    return;
  }
  int mid = (lo + hi) / 2;
  update_range(s, e, x, lo, mid, 2 * node + 1);
  update_range(s, e, x, mid + 1, hi, 2 * node + 2);
  st[node] = min(st[2 * node + 1], st[2 * node + 2]);
}
 
int query(int s, int e, int lo = 0, int hi = -1, int node = 0) {
  if (hi == -1) hi = N - 1;
  push(lo, hi, node);
  if (hi < s || lo > e) return 0;
  if (lo >= s && hi <= e) return st[node];
  int mid = (lo + hi) / 2;
  return min(query(s, e, lo, mid, 2 * node + 1),
             query(s, e, mid + 1, hi, 2 * node + 2));
}
 
void make_ordering() {
  lzysiz = 1048576;
  N = n + q;
  lazy.resize(lzysiz);
  st.resize(lzysiz);
  for (int i = 0; i < N; i++) {
    update_range(i, i, INF);
  }
 
  dfs_ord(0, -1);
}
 
void init_segtree() {
  for (int i = 0; i < n; i++) {
    curind[i] = -1;
  }
 
  curind[0] = sten0[curcol[0]].x + curfreq0[curcol[0]];
  curfreq0[curcol[0]]++;
 
  for (int i = 1; i < n; i++) {
    curind[i] = sten[from[i]][curcol[i]].x + curfreq[from[i]][curcol[i]];
    curfreq[from[i]][curcol[i]]++;
  }
 
  for (int i = 0; i < n; i++) {
    int indupd;
    indupd = curind[i];
    update_range(indupd, indupd, wt[i] - INF);
    // we are subtracting INF cuz we are using that node right now
  }
 
  // now we need to subtract INF from all nodes that share the same color as us
  // rn and are our children
 
  // okay we need to manually make sure we never touch node 0
 
  int endind = 0;
  for (auto& x : sten0) {
    endind = max(endind, x.y.y);
  }
 
  // update_range(0, endind, 1e9);
 
  for (int i = 0; i < n; i++) {
    if (colcnt[i][curcol[i]] != 0) {
      int lupd, rupd;
      lupd = sten[i][curcol[i]].x;
      rupd = sten[i][curcol[i]].y;
      update_range(lupd, rupd, INF);
    }
  }
}
 
inline void init_qrys() {
  make_ordering();
  init_segtree();
}
 
void solvebrute() {
  MSETI use;
 
  for (int i = 0; i < n; i++) {
    for (auto& x : adj[i]) {
      if (x.x > i) continue;
      // use.insert(x.y);
      if(curcol[x.x] != curcol[i]) {
        use.insert(x.y);
      }
    }
  }
 
  for (int i = 0; i < q; i++) {
    int a, b;
    cin >> a >> b;
    a--;
 
    for (auto& x : adj[a]) {
      if (curcol[x.x] == b) {
        // why
        // because this is an edge that previously existed
        // and now they are the same type
        // so we need to remove it
        auto it = use.find(x.y);
        use.erase(it);
      }
    }
 
    for (auto& x : adj[a]) {
      if (curcol[x.x] == curcol[a]) {
        // why
        // because this is an edge that previously didn't exist
        // since they had same color
        // but now they have the same color
        // so...  
        use.insert(x.y);
      }
    }
 
    if (!use.empty()) {
      cout << *use.begin() << '\n';
    }
 
    curcol[a] = b;
  }
}
 
int main() {
#ifndef ONLINE_JUDGE
  freopen("grass.in", "r", stdin);
  freopen("grass.out", "w", stdout);
#endif
  cin.sync_with_stdio(0);
  cin.tie(0);
 
  cin >> n >> m >> k >> q;
 
  init();
 
  for (int i = 0; i < m; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    u--;
    v--;
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
    edg[i] = (MP(w, MP(u, v)));
  }
 
  for (int i = 0; i < n; i++) {
    cin >> curcol[i];
  }
 
  sort(all(edg));
 
  int cnt = 0;
 
  for (int i = 0; i < m and cnt < n - 1; i++) {
    auto cur = edg[i];
    int u, v, w;
    u = cur.y.x;
    v = cur.y.y;
    w = cur.x;
    if (!same(u, v)) {
      cnt++;
      merge(u, v);
      mst[u].PB(MP(v, w));
      mst[v].PB(MP(u, w));
    }
  }
 
  int mxdeg = 0;
  for (int i = 0; i < n; i++) {
    mxdeg = max(mxdeg, (int)adj[i].size());
  }
 
  if (mxdeg <= 10) {
    solvebrute();
    return 0;
  }
 
  // we now have the mst
  // now we need to create the ordering
  // sed lyfe :( :( :(
  // i think first we need to read the queries
  // and then order based on that
 
  dfs_par(0, -1);
  // we now have everybody's parents
  cnt0[--curcol[0]]++;
  for (int i = 1; i < n; i++) {
    colcnt[from[i]][--curcol[i]]++;
  }
 
  for (int i = 0; i < q; i++) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    qrys[i] = MP(a, b);
    if (a) {
      colcnt[from[a]][b]++;
    } else {
      cnt0[b]++;
    }
  }
 
  // okay we have the information we need to make the ordering i think
  init_qrys();  // this is prep work for the queries
 
  VI retqry(q);
 
  for (int i = 0; i < q; i++) {
    // alright ill fill this in later lmao
    int cur_node, n_color;
    cur_node = qrys[i].x;
    n_color = qrys[i].y;
    // using long variable names cuz im too dumbosity to remember what to do
 
    // what do we have to do now
    // we have to increase current index of cur_node by INF (done)
    // decrease the value at the new index by INF (done)
    // decrease all of your children that are the same color by INF
    // increase all of your new children that are the same color by INF
    // the print the answer to global min of segtree
 
    int c_ind = curind[cur_node];
    int c_col = curcol[cur_node];
 
    update_range(c_ind, c_ind, INF);
    // now we need to determine new index
 
    int n_ind;
    if (cur_node == 0) {
      n_ind = curfreq0[n_color] + sten0[n_color].x;
      curfreq0[n_color]++;
    } else {
      n_ind =
          curfreq[from[cur_node]][n_color] + sten[from[cur_node]][n_color].x;
      curfreq[from[cur_node]][n_color]++;
    }
    curind[cur_node] = n_ind;
    curcol[cur_node] = n_color;
    update_range(n_ind, n_ind, wt[cur_node] - INF);
 
    int lupd, rupd;
 
    if (colcnt[cur_node][c_col] > 0) {
      lupd = sten[cur_node][c_col].x;
      rupd = sten[cur_node][c_col].y;
      update_range(lupd, rupd, -INF);
    }
 
    if (colcnt[cur_node][n_color] > 0) {
      lupd = sten[cur_node][n_color].x;
      rupd = sten[cur_node][n_color].y;
      update_range(lupd, rupd, INF);
    }
    int ret = query(0, N - 1);
    // cout << ret << '\n';
    retqry[i] = ret;
  }
 
  for (int i = 0; i < q; i++) {
    cout << retqry[i] << '\n';
  }
 
  return 0;
}