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: Accepted)

n, k = gets.split.map(&:to_i)

if k == 1 && n == 1
  puts 'YES'
elsif k>=n
  puts 'NO'
else
  # 4 => 3
  # 5 => 4
  # 6 =>
  if n % 2 == 0
    if k > (n / 2)
      puts 'NO'
    else
      puts 'YES'
    end
  else
    if k > (n / 2) + 1
      puts 'NO'
    else
      puts 'YES'
    end
  end
end