why he made this condition in his code in this problem : https://codeforces.net/contest/1512/problem/E if(s — i >= 1LL * (len — 1) * len / 2 && len > 0) i am talking about s-i =>(len-1)*(len)/2 code :

include <bits/stdc++.h>

define ll long long

define sz(x) ((int) (x).size())

define all(x) (x).begin(), (x).end()

define vi vector

define pii pair<int, int>

define rep(i, a, b) for(int i = (a); i < (b); i++)

using namespace std; template using minpq = priority_queue<T, vector, greater>;

void solve() { int n, l, r; ll s; cin >> n >> l >> r >> s; vector ve, ve2; int len = r — l + 1; for(int i = n; i >= 1; i--) { if(s — i >= 1LL * (len — 1) * len / 2 && len > 0) { ve.push_back(i); len--; s -= i; }else { ve2.push_back(i); } } if(s > 0) { cout << -1 << '\n'; return; } rep(i, 0, l — 1) { cout << ve2.back() << ' '; ve2.pop_back(); } for(int x : ve) { cout << x << ' '; } for(int x : ve2) { cout << x << ' '; } cout << '\n'; }

int main() { ios::sync_with_stdio(false); cin.tie(0); int te; cin >> te; while(te--) solve(); }