#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long long int k) {
    long long int k1=k;
    k--;
    long long int fe=(k*(k+1))/2;
   fe=2*fe+1;
    long long int le=fe+(k1-1)*2;
    long long int sum=(k1*(fe+le))/2;
    return sum;
}

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