#include <bits/stdc++.h>

using namespace std;

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

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