#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long int k) {
    // Return the sum of the elements of the k'th group.
      long int n,sum,i;
    n=k*(k-1)+1;
    sum=0;
    while(k--)
    {
        //n=n+2;
        sum=sum+n;
        n+=2;
    }
    return sum;
}

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