#include <bits/stdc++.h>

using namespace std;

int main() {
    int k;
    cin >> k;
    long long n=(long long) (k)*(k-1)/2;
    long long a=(long long) 1+n*2;
    cout<<(long long) (a+(a+2*k-2))*k/2<<endl;
    return 0;
}