#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    
  long long before = k*(k-1)/2;
  
  long long first = before*2 + 1;
  
  return k*(k-1) + k * first;
  
}

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