#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    // Return the sum of the elements of the k'th group.
    long long x=k*(k-1)+1;long long s=0;
    while(k--)
    {s+=x;
        x+=2;
    }
    return s;
}

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