func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   using pii = pair<int, ll>;   int n, m;   vector<pii> coupons;   bool comp(pii a, pii b) { return a.second > b.second; }   ll getlen(ll x) {     if (x % 2 == 1) return x * (x - 1) / 2 + 1;     return x * (x - 1) / 2 + x / 2;   }   int main() {     cin >> n >> m;     ll low = 0, high = n;     while (low < high) {       ll mid = (low + high + 1) / 2;       if (getlen(mid) <= n) {         low = mid;       } else {         high = mid - 1;       }     }     for (int i = 0; i < m; i++) {       ll q, w;       cin >> q >> w;       coupons.push_back({q, w});     }     sort(coupons.begin(), coupons.end(), comp);     ll ans = 0;     for (int i = 0; i < low && i < m; i++) {       ans += coupons[i].second;     }     cout << ans << endl;   }   