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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php /*atcoder.php*/

$at = new Atcoder();
$at->main();
unset($at);

class Atcoder{
	private function arrayIn(){
		$buf = explode(" ", fgets(STDIN));
		return $this->killNewLine($buf);
	}
	private function killNewLine($buf = null){
		$buf = str_replace("\r\n", "", $buf);
		$buf = str_replace("\n", "", $buf);
		$buf = str_replace("\r", "", $buf);
		return $buf;
	}

	public function main(){
		$s = $this->arrayIn();
		
		$n = $s[0];
		$k = $s[1];

		if(0 != ($n % 2)){
			$n++;
		}

switch ($n){
case ( 2 ) :
 if ( 1  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 4 ) :
 if ( 2  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 6 ) :
 if ( 3  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 8 ) :
 if ( 4  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 10 ) :
 if ( 5  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 12 ) :
 if ( 6  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 14 ) :
 if ( 7  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 16 ) :
 if ( 8  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 18 ) :
 if ( 9  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 20 ) :
 if ( 10  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 22 ) :
 if ( 11  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 24 ) :
 if ( 12  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 26 ) :
 if ( 13  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 28 ) :
 if ( 14  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 30 ) :
 if ( 15  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 32 ) :
 if ( 16  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 34 ) :
 if ( 17  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 36 ) :
 if ( 18  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 38 ) :
 if ( 19  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 40 ) :
 if ( 20  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 42 ) :
 if ( 21  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 44 ) :
 if ( 22  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 46 ) :
 if ( 23  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 48 ) :
 if ( 24  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 50 ) :
 if ( 25  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 52 ) :
 if ( 26  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 54 ) :
 if ( 27  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 56 ) :
 if ( 28  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 58 ) :
 if ( 29  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 60 ) :
 if ( 30  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 62 ) :
 if ( 31  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 64 ) :
 if ( 32  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 66 ) :
 if ( 33  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 68 ) :
 if ( 34  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 70 ) :
 if ( 35  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 72 ) :
 if ( 36  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 74 ) :
 if ( 37  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 76 ) :
 if ( 38  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 78 ) :
 if ( 39  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 80 ) :
 if ( 40  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 82 ) :
 if ( 41  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 84 ) :
 if ( 42  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 86 ) :
 if ( 43  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 88 ) :
 if ( 44  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 90 ) :
 if ( 45  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 92 ) :
 if ( 46  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 94 ) :
 if ( 47  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 96 ) :
 if ( 48  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 98 ) :
 if ( 49  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
 break;
case ( 100 ) :
 if ( 50  >= $k ) { echo "YES\n"; }else{ echo "NO\n"; }
}

	}
}
?>