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: Runtime Error)

n, k = STDIN.read.split(' ').map(&:to_i)

case
when k > n
  out = 'NO'
when k < 0
  out = 'NO'
when k == 0
  out = 'YES'
else
  max = case
  when n % k = 0
    n / 2
  when n % k = 1
    n / 2 + 1
  end

  out = if k <= max
    'YES'
  else
    'NO'
  end
end

puts out