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

ll sumOfGroup(ll k) {
   
    ll sum = 0;
    ll num = (k)*(k-1)/2;
   num = (2*num )+1;
   while(k--)
   {
       sum+=num;
       num+=2;
   }
    
    return sum;
    
    
}

int main() {
    ll k;
    cin >> k;
    ll answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}