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);
		int k = in.nextInt();
		long sum = 0 ;
		for(int i = 1 ; i < 1000000 ; i++){
			if(i % 2 != 0){
			if(i == k){

				int n = 0 ;
				for(int j = i ; n < k; j+=2){
					sum = sum + j;
					n++;
					if(n  == k ){
						break;
					}
				}
			}
			else
				continue;
		}
			else 
				continue;
		}
		System.out.println(sum);
    }
}