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 Python (3.4.3) (judge verdict: Wrong Answer)

if __name__==("__main__"):
  text = input()
 
  text = text.split(" ")
  N = int(text[0])
  K = int(text[1])
 
  ans = int((N * (N - 1)) / 2) - int(N / 2)
  print(ans)
  if ans >= K:
    print("YES")
  else:
    print("NO")