#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(int k) {
    long long f = ((long long) k * (k-1LL)) + 1LL;
    long long acc = f;
    for (int i = 1; i < k; i++) {
        f = f + 2LL;
        acc += f;
    }
    return acc;
}

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