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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main()
{

    int N;
    int K;
    int ans;

    scanf("%d %d\n",&N,&K);

    ans=-1;

    if(N>K){
        if(N%2==0){
            if(K<=N/2){
                ans=1;
            }
        }
        else{
            if(K<=(N+1)/2){
                ans=1;
            }
        }
    }

    if(ans>0){
        printf("YES\n");
    }
    else
    {
        printf("NO\n");
    }
    
    return 0;
}