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

public class Solution {

    static long sumOfGroup(int x) {
        // Return the sum of the elements of the k'th group.
	    long k=x;
		   long sum1=(k*(k+1))/2;
	        sum1=sum1*sum1;
	        long sum2=((k-1)*(k))/2;
	        sum2=sum2*sum2;
	        return(sum1-sum2);
    }

    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();
    }
}