#include <bits/stdc++.h>

using namespace std;


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