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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;

class Program{
  static void Main(string[] args) {
    int[] x = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
    int n = x[0];
    int k = x[1];
    int cnt = 0;
    for(int i = 1; i <= n; i+=2) cnt ++;
    Console.WriteLine(cnt>=k ? "YES" : "NO");
  }
}