///Number Groups
///https://www.hackerrank.com/contests/101hack52/challenges/number-groups
#include <iostream>

using namespace std;
typedef long long ll;
ll k,before,ans;
int main()
{
    ios_base::sync_with_stdio(0);
    cin>>k;
    before=(k-1)*k/2;
    ll last=before*2-1;
    last+=2LL;
    while(k--)
    {
        ans+=last;
        last+=2LL;
    }
    cout<<ans;
    return 0;
}