#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    unsigned long long  s = (1ULL*k*k - k + 1) + (1ULL*(k+1)*(k+1) - (k+1) - 1);
    s = (k * s)/2;
    return (long)s;
}

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