#include <bits/stdc++.h>

using namespace std;

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

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