func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long int n;     int k, w, total;     cin >> k >> n >> w;     total = k * w * (w + 1) / 2 - n;     if (total <= 0) {       cout <<  0  << endl;     } else {       cout << total << endl;     }   }   