#include <bits/stdc++.h>

using namespace std;
long summ(long k){
    long a = k*(2+(k-1));
    a = a/2;
    return a;
}
long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long x = summ(k-1);
    //cout<<x<<"\n";
    long y = x*2;
    long sum = 0;
    y++;
    for(long i=0;i<k;i++){
        sum += y;
        y +=2;
    }
    return sum;
}

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