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 Ruby (2.3.3) (judge verdict: Wrong Answer)

n,k = gets.split(" ").map!{|i| i.to_i}
sum = 0
1.upto(n) do |p|
 p.upto(n) do |j|
  if (j - p).abs > 1
    sum += 1
end
end
end
if sum >= k 
 puts 'Yes'
else puts 'No'
end