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 <iostream>
#include <algorithm>
#include <vector>
#include <utility>
using namespace std;

typedef unsigned long ul;
typedef long long int ll;
typedef pair<ll, ll> P;
#define pb push_back
#define mp make_pair
#define REP(i,n) REPN(i,0,n)
#define REPN(i,m,n) for(int i=m; i<(n); i++)
#define ALL(a) (a).begin(),(a).end()
#define dump(x) cout << #x << " = " << (x) << endl

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, k;
    cin >> n >> k;
    if ((n+1)/2 < k) {
        cout << "NO" << '\n';
    } else {
        cout << "YES" << '\n';
    }
}