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 heapq
from sys import stdin
input = stdin.readline

#入力
# s = input()[0:-1]
# n = int(input())
n,k = map(int, input().split())
# a = list(map(int,input().split()))
# a = [int(input()) for i in range()]


# ab=[]
# for i in range():
#     a,b = map(int, input().split())
#     ab.append([a,b])


     
def main():
    if (n+2-1)//2 <k:
        print("NO")
    else:
        print("YES")

if __name__ == '__main__':
    main()