func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long n;     cin >> n;     n = (n * (n - 1)) / 2 + (((n * (n - 1)) / 2) * ((2 * n - 1))) / 3 - 2;     cout << n << endl;     return 0;   }   