#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    
      if(k==1)
        return 1;
   long a=k*(k-1)+1;
    long sum=(k*(2*a+(k-1)*2)/2);
    return sum;
}


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