func_code_string: #include <bits/stdc++.h>   using namespace std;   long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }   long long lcm(long long a, long long b) { return a * (b / gcd(a, b)); }   const int N = 100005;   void solve() {     long long n;     cin >> n;     long long ans = 1;     for (long long i = 2; i <= n; i++) {       ans = ans + 4 * (i - 1);     }     cout << ans;   }   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int TESTS = 1;     while (TESTS--) {       solve();     }     cerr <<   nTime elapsed:   << 1000 * clock() / CLOCKS_PER_SEC <<  ms n ;     return 0;   }   