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
list ($N, $K) = explode(" ", trim(fgets(STDIN)));

if ($N % 2 == 1) {
    $N++;
}

echo ($N / 2 >= $K ? 'YES' : 'NO') . "\n";