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