#include <bits/stdc++.h>
#include<iostream>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long num=1,sum=0;
    for(long i=0;i<k;i++)
    {
        num+=2*i;
    }
    for(long i=0;i<k;i++)
    {
        sum+=(num+(2*i));       
    }
    return sum;
}

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