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


$input = explode(" ", trim(fgets(STDIN)));  

// $input = array(99, 0); //N K
// var_dump($input);
/*
1からNの間の値が、奇数でJ個あり、J<＝Kである


*/


$N = $input[0];
$K = $input[1];

$maxEvenNum = $N%2 == 0 ? $N-1 : $N;
// var_dump($maxEvenNum);

$J = (($maxEvenNum-1) / 2) + 1;
// var_dump($J);

if($K <= $J) {
	print 'YES';
} else {
	print 'NO';
}