#include <bits/stdc++.h>

using namespace std;

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

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