15分求助，找不着错哪了

#include<bits/stdc++.h>
using namespace std;

//二分+前缀和

const int N = 1.e6;
int n;//矿石个数
int m;//区间个数
int s;//标志值
int rock[N][3];//记录石头
int itval[N][3];//记录区间
long long p[N];//记录前缀
long long Q[N];//记录前缀
int ans;
long long need;//放每次的结果

bool check(int w) {
    long long sums = 0;
    for (int i = 1; i <= n; i++) {
        if (rock[i][1] >= w) {
            {
                p[i] = 1 + p[i - 1];
                Q[i] = rock[i][2] + Q[i - 1];
            }
        }
        else {
            p[i] = p[i - 1];
            Q[i] = Q[i - 1];
        }
    }
    for (int i = 1; i <= m; i++) {

        int left = itval[i][1] - 1;
        int right = itval[i][2];

        sums += (p[right] - p[left]) * (Q[right] - Q[left]);

    }
    need = llabs(s - sums);
    if (sums > s)return true;
    return false;
}

int main() {
    cin >> n >> m >> s;
    ans = 1.e6;
    int maxM = 0;
    int minM = 1.e6;
    for (int i = 1; i <= n; i++) {
        cin >> rock[i][1] >> rock[i][2];
        if (rock[i][1] > maxM)maxM = rock[i][1];
        if (rock[i][1] < minM)minM = rock[i][1];

    }
    for (int i = 1; i <= m; i++) {
        cin >> itval[i][1] >> itval[i][2];
    }

    int L = minM - 1;
    int R = maxM + 1;
    while (L + 1 < R) {
        int mid = (L + R) / 2;
        if (check(mid))L = mid;
        else {
            R = mid;
        }
        ans = need < ans ? need : ans;
    }
    cout << ans << endl;
}