#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) 
{
    // Return the sum of the elements of the k'th group.
    int temp=k-1,j;
    int temp1=0;
    int i,sum=0;
    for(i=1;i<=temp;i++)
    {
        temp1=temp1+i;
    }
    temp1=(temp1*2)+1;
    for(i=0,j=temp1;i<k;i++,j+=2)
    {
        sum+=j;
    }
    return sum;
}

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