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: Accepted)

#include<stdio.h>

int main(void)
{
        int n,k,ans;
        scanf("%d %d",&n,&k);

        if(n % 2 == 0 && n / 2  >= k) {
                printf("YES\n");
        } else if(n % 2 == 1 && n / 2 + 1 >= k) {
                printf("YES\n");
        } else {
                printf("NO\n");
        }

        return 0;
}