#include<bits/stdc++.h>
using namespace std;
#define ll long long
int a[1000000];

int main()
{
    ll k;
    cin>>k;
    ll ans=k*(k-1)+1;
    ll sum=0;
    for(ll i=0;i<k;i++)
    {
        sum+=ans;
        ans+=2;
    }
    cout<<sum<<endl;

}