#include <bits/stdc++.h>

using namespace std;



int main() {
    
    long long  k,ans=0,ans1=0,answer=0;
    cin >> k;
    ans=(k*(k-1))+1;
    ans1=ans+(k-1)*2;
    answer=k*(ans+ans1)/2;
    cout << answer << endl;
    return 0;
}