import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long n = k-1;
        n = (long)((n * (n+1))/2);
        long a = (2*n+1);
        n = k;
        long ans = (long)((n)*(long)(2*a+(n-1)*2)/2);
        return ans;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}