func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<pair<int, int> > v;   int main(void) {     int n, m, a, b;     scanf( %d%d , &n, &m);     for (int i = 0; i < m; i++) {       scanf( %d%d , &a, &b);       v.push_back(make_pair(b, a));     }     sort(v.rbegin(), v.rend());     long long ans = 0;     int i = 0;     while (n) {       int del = min(n, v[i].second);       ans += (long long)del * v[i].first;       n -= del;       i++;       if (i == v.size()) break;     }     printf( %lld n , ans);   }   