#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

long sumOfGroup(int k) {
    ll q = (k - 1) * (ll)k / 2;
    ll ans = 0;
    while (k--){
        ans += 2 * q + 1;
        q++;
    }
    return ans;
}

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