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 Ruby (2.3.3) (judge verdict: Wrong Answer)

# 1以上N以下の異なる整数を、差が1の整数をともに選ばないようにK個選ぶことができるか判定する関数
# @param n
# @param k
# @return canGet
def canGetK(n, k)
  mirginNum = (n - 1) / 2
  canGet = (mirginNum + 1) >= k ? 'YES' : 'NO'
end

if __FILE__ == $0
  input = gets.chomp
  n,k = input.split(' ').first.to_i, input.split(' ').last.to_i
  p canGetK(n, k)
end