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 <cstdio>
#include <vector>
#include <stack>
#include <iostream>
#include <string>
#include <tuple>
#include <random>
#include <map>
#include <queue>
#include <set>
#include <complex>
#include <algorithm>
#include <cassert>
#include <iterator>
#include <numeric>
#include <cmath>
#include <stdio.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;

const double eps = 1e-8;

const ll INF = 1e15;
const ll MOD = 1e9 + 7;

int main() {
	ll N, K;
	cin >> N >> K;
	if ((N + 1) / 2 >= K)
		cout << "YES" << endl;
	else
		cout << "NO" << endl;
	return 0;
}