#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    long startnum = k * (k - 1) + 1;
    long current = startnum;
    long result = current;
    
    for (int i = 1; i < k; i++)
    {
        current = startnum + i*2;
        result += current;
    }
        
    return result;
}

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