#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long long temp;
    temp = k*(k-1);
    temp/=2;
    long long f = 2*temp+1;
    long long sum = 0;
    for(int i = 0;i<k;i++){
        sum+=f;
        f+=2;
    }
    return sum;
}

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