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.Collections.Generic;
using System.Linq;
using System.Text;

namespace atcorder_yahoo
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] dataArr = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse); 
            int maxNum = dataArr[0];
            int cnt = dataArr[1];

            int getCnt = 0;

            for(int i = 1; i <= maxNum; i += 2)
            {
                getCnt++;
            }

            string ret = "NO";
            if(cnt <= getCnt)
            {
                ret = "YES";
            }

            Console.WriteLine(ret);
        }
    }
}