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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int gcd(int a, int b) {  
  return b != 0 ? gcd(b, a % b) : a;
}//MAX
int lcm(int a, int b) { 
   return a * b / gcd(a, b);
   }
//MIN

 main() {
int n,k;
cin >> n >> k;
int che = n-n/2;
if(che>=k)cout <<"YES"<<endl;
else cout <<"NO"<<endl;

}