#include<bits/stdc++.h>
using namespace std;

#define ll long long

int main()
{
    ll n, nn, sum = 0;
    cin>>n;
    nn  = n;
    n = (n*(n-1))+1;

    for(ll i = 0; i<nn; i++, n+=2)
        sum+=n;
    cout<<sum<<endl;

}