#include <bits/stdc++.h>

using namespace std;

int64_t sumOfGroup(int64_t k) {
    return (k-1)*k + ((k-1)*k + 1)*k;
}

int main() {
    int64_t k;
    cin >> k;
    int64_t answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}