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

public class Solution {

    static long sumOfGroup(Long k) {
        // Return the sum of the elements of the k'th group
        long n=(k*(k-1))+1;
        long i=0;
        long res=0;
        while(i<k)
        {
            
            res+=n;;
            i++;
            n+=2;
        }
        return res;
    }

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