Problem:
Score : 100 points

Problem Statement

Determine if we can choose K different integers between 1 and N (inclusive) so that no two of them differ by 1.

Constraints

1\leq N,K\leq 100

N and K are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

If we can choose K integers as above, print YES; otherwise, print NO.

Sample Input 1

3 2

Sample Output 1

YES

We can choose 1 and 3.

Sample Input 2

5 5

Sample Output 2

NO

Sample Input 3

31 10

Sample Output 3

YES

Sample Input 4

10 90

Sample Output 4

NO

Solution in PHP (5.6.30) (judge verdict: Accepted)

<?php
$inp = fgets(STDIN);
$nk = explode(" ", $inp);
$N = $nk[0];
$K = $nk[1];
$max = ceil($N/2);
if($max >= $K) {
	echo 'YES';
} else {
	echo 'NO';
}