Hello, I'm a pretty beginner with segment trees and I'm in doubt on this problem, I can build the tree but the queries for look for the right interval with the biggest sum is wrong, can someone point out what is wrong with my method func. Thanks in advance.

Problem Statement

#include <iostream>
#include <fstream>
#include <vector>
#include <list>
#include <deque>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <utility>
#include <functional>
#include <valarray>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <climits>

using namespace std;

#define REP(i, n) for(i = 0; i < (n); i++)
#define FOR(i, a, n) for(i = a; i < n; i++)
#define REV(i, a, n) for(i = a; i > n; i--)

template<typename T> T gcd(T a, T b) {
    if(!b) return a;
    return gcd(b, a % b);
}
template<typename T> T lcm(T a, T b) {
    return a * b / gcd(a, b);
}

typedef long long ll;
typedef long double ld;

#define MAXN 5000010
#define INF 1000001000

int n, a[MAXN], t[4*MAXN];
int b, c, i, m, tmp, x;

void build (int a[], int v, int tl, int tr) {
    if (tl == tr)
        t[v] = a[tl];
    else {
        int tm = (tl + tr) / 2;
        build (a, v*2, tl, tm);
        build (a, v*2+1, tm+1, tr);
        t[v] = t[v*2] + t[v*2+1];
    }
}

int func(int v, int tl, int tr, int l, int r) {
    if(l > tr || r < tl) {
        return -INF;
    }
    if(tl >= l && tr <= r) {
        return t[v];
    }
    int tm = (tl + tr) / 2;
    int p1 = func(2 * v, tl, (tl + tr) / 2, l, r);
    int p2 = func(2 * v + 1, ((tl + tr) / 2) + 1, tr, l, r);

    if(p1 > p2) return p1;
    else return p2;
}
int main(void) {
    freopen("i.in", "r", stdin);
    scanf("%d", &x);
    REP(i, x) {
        scanf("%d", &a[i+1]);
    }
    build(a, 1, 1, x+1);    
    scanf("%d", &m);
    REP(i, m) {
        scanf("%d%d", &b, &c);
        printf("%d\n", func(1, 1, x+1, b, c));
    }
    return 0;
}