#include <bits/stdc++.h>

using namespace std;

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

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