#include <bits/stdc++.h>

using namespace std;

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

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