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

public class Solution {

    static long sumOfGroup(int k) {
       long a,i,n=k-1;
         a=k*n;
            a+=1;
      long  sum=a;
        for(i=1;i<k;i++)
        {
           a=a+2; 
           sum=sum+a;

        }
        return sum;
    }

    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();
    }
}