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 t = (long)k*(k-1)+1;
        long a = t*k;
        long b=0,sum = 0;
        
        for(int i=1;i<k;i++){
            b+=2*i;
        }
        
        sum = a+b;
        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();
    }
}