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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(long long int i=0;i<n;++i)
typedef long long int ll;

int main(){

    int n,k;
    cin  >> n >> k;

    if(n==1){
        cout << "NO" << endl;
        return 0;
    }

    if(k<=n/2+1){
        cout << "YES"<< endl;
    }else{
        cout << "NO" << endl;
    }

    return 0;
}