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>
#include <stdbool.h>

#define	BUFFER_LENGTH	(256)

int
main(int argc, const char *argv[])
{
	char buffer[BUFFER_LENGTH];
	int n;
	int k;

	(void)fgets(buffer, sizeof(buffer), stdin);
	(void)sscanf(buffer, "%d %d\n", &n, &k);

	(void)printf("%s\n", (k * 2 <= n + 1) ? "YES": "NO");

	return 0;
}