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 Python (3.4.3) (judge verdict: Accepted)

import numpy as np
n,k = list(map(int, input().split()))

if n%2 == 0:
    if (n//2) >= k:
        print('YES')
    else:
        print('NO')
else:
    if (n//2 + 1) >= k:
        print('YES')
    else:
        print('NO')