#include <bits/stdc++.h>

using namespace std;

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

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