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
fscanf(STDIN, '%d %d', $n, $k);
echo ($n == 1 && $k == 1) || ($n > 2 && $k == 2) || ($n - ($k + ($k - 1)) >= 0) ? 'YES' : 'NO' . "\n";