#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    int i=1,j=1;
    long sum,y=1;
        while(i<=k)
    {
        if(i!=k)    
        while(j<=i)
        {
            y=y+2;
            j=j+1;
        }
        if(i==k)
        {
            while(j<=i)
            {
                sum=sum+y;
                y=y+2;
                j=j+1;
            }
        }
        i=i+1;
        j=1;
    }
    return(sum);
}

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