#include <bits/stdc++.h>

using namespace std;



int main() {
    long long int k;
    cin >> k;
    long long answer =0;
    k--;
    long long int n=k*(k+1)/2;
    k++;
    n=n*2+1;
    for(long long int i=0;i<k;i++,n+=2)
        answer+=n;
    cout<<answer;
    return 0;
}