#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long INF = 1e+14;
const long double eps = 1e-8;
const long double pi = acos(-1.0);
void Yes() {
  cout << "Yes" << endl;
  exit(0);
}
void No() {
  cout << "No" << endl;
  exit(0);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long n;
  cin >> n;
  long long dp[110];
  dp[1] = 1;
  for (long long i = 2; i <= n; i++) {
    dp[i] = dp[i - 1] + 4 * (i - 1);
  }
  cout << dp[n] << endl;
  return 0;
}
