#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long long int start = 2*((((k-1)*(k))/2)+1)-1;
    long long int ans = (k*(start+(k-1)));
    return ans;
    
}

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