#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    if(k == 1)
        return 1;
    long initial = 1;
    for(int i = 1; i < k; i++){
        initial = initial + (2 * i);
    }
    long max = initial;
    for(int i = 1; i < k; i++){
        max += (initial + 2);
        initial += 2;
    }
    return max;
}

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