func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long int n, m, x, y, i, s = 0, k = 0;     vector<pair<long long int, long long int> > v;     cin >> n >> m;     for (i = 0; i < m; i++) {       cin >> x >> y;       v.push_back(make_pair(y, x));     }     sort(v.begin(), v.end());     for (i = v.size() - 1; i >= 0; i--) {       if (n > 0) {         if (v[i].second >= n) {           s = s + n * v[i].first;           n = 0;         } else {           s = s + v[i].second * v[i].first;           n = n - v[i].second;         }       } else {         k = -1;         cout << s << endl;         break;       }     }     if (k == 0) cout << s << endl;   }   