#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long sum = 1;
    for(int i = 2; i <= k; i++){
      sum += 2 * (i - 1);
    }
    long ans = sum;
    for(int i = 2; i <= k; i++){
      ans += (sum + 2 * (i - 1));
    }
    return ans;
}

int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}