#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long firstNumber=pow((k-1),2)+(k-1)+1,sum;
    sum=firstNumber;
    //cout<<firstNumber<<"\t"<<sum<<endl;
    for(int i=0;i<k-1 && k!=1;i+=1)
    {
        sum+=firstNumber+2;
        firstNumber+=2;
        //cout<<firstNumber<<" : "<<sum<<endl;
    }
    return sum;
}

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