func_code_string: #include <bits/stdc++.h>   using namespace std;   void solve(void) {     int N;     long int s = 0;     cin >> N;     for (int i = 2; i <= N; i++) s += i - 1;     cout << s * 6 * 2 + 1 << endl;   }   int main(int argc, char const *argv[]) {     solve();     return 0;   }   