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 Scala (2.11.7) (judge verdict: Accepted)

import scala.math.ceil

object Main {
  val sc = new java.util.Scanner(System.in)

  def sin(n: Int): Seq[Int] = Seq.fill(n)(sc.nextInt())

  def iin(): Int = sc.nextLine().toInt

  def main(args: Array[String]): Unit = {
    val n, k = sc.nextDouble()

    println( if(ceil(n / 2) >= k) "YES" else "NO" )
  }
}