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

public class Solution {

    static long sumOfGroup(int k) {
        if(k==1)
        {
            return 1;
        }
        else
        {
            long start = 0;
            for(long i = 1;i<=k-1;i++)
            {
                start += i;
            }
            start *= 2;
            start += 1;
            
            long sum = 0;
            for(int i = 0;i<k;i++)
            {
                sum += start;
                start += 2;
            }
            return sum;
        }
        // Return the sum of the elements of the k'th group.
    }

    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();
    }
}