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: Wrong Answer)

<?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++;
		}
		if(2 >= $n){
			echo "NO\n";
			return false;
		}
		if(($n / 2) >= $k){
			echo "YES\n";
		}else{
			echo "NO\n";
		}

		return true;

	}
}
?>