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
//error_reporting(0);
//$N = trim(fgets(STDIN));
list($N,$K) =  explode(" ",trim(fgets(STDIN)));
//$X = explode(" ",trim(fgets(STDIN)));

if (ceil($N/2) >= $K) {
  printf("YES\n");
}
else {
  printf("NO\n");
}