#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    long long st = 0;
    for (int i = 1; i < k; i++)
        st += i;
    long long sum = 0;
    return k*(2*st+1) + k*(k-1);
    //for (int i = st; i <= st + k - 1; i++)
        //sum += 2*i+1;
    return sum;
}

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