#include <bits/stdc++.h>

using namespace std;

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

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