和KesdiaelKen的题解的代码本质基本一样，但就是过不了样例

#include <bits/stdc++.h>
using namespace std;
int n, s, c[10005], y[10005];
long long ans;
int main() {
    cin >> n >> s;
    for (int i = 1; i <= n; i++) cin >> c[i] >> y[i];
    for (int i = 1; i <= n; i++) {
        long long sum = 0, money = 1005000;
        for (int j = i; j >= 1; j--) {
            sum += s;
            money = min(money, sum + c[j]);
        }
        ans += money * y[i];
    }
    cout << ans;
    return 0;
}