Score : 100 points
Determine if we can choose K different integers between 1 and N (inclusive) so that no two of them differ by 1.
Input is given from Standard Input in the following format:
N K
If we can choose K integers as above, print YES
; otherwise, print NO
.
3 2
YES
We can choose 1 and 3.
5 5
NO
31 10
YES
10 90
NO