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)

c,t,d[4010][4010];char s[4010];i;main(j){for(**d=scanf("%s",s);s[i/2];i++)for(j=c+=s[i]?t++,s[i]-48:0;j>i+c-2*t&&~j;j--)d[i+1][j]=(d[i][j]+d[i][j-1])%998244353;printf("%d",d[i][c]);}