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

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long k = in.nextInt();
        long suite = k*(k+1)/2;
        long answer = 0;
        for (long h = suite*2-(k*2)+1; h <= suite*2; h++) {
            if(h%2==1){
					answer =answer + h;
            }
		}
        System.out.println(answer);
        in.close();
    }
}