#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int dp[n + 1];
  dp[1] = 1;
  dp[2] = 5;
  for (int i = 3; i <= n; i++) {
    dp[i] = dp[i - 1] + (i - 1) * 4;
  }
  cout << dp[n] << endl;
  return 0;
}
