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 <cmath>
#include <string>
#include <algorithm>
#include <set>
#include <vector>
#include <map>
#include <list>
#include <stack>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#define mkp(a, b) make_pair(a, b)
#define pb(t) push_back(t)
#define ft first
#define sc second
#define pt(num) cout << num << "\n"
#define moC(a, s, b) (a)=((a)s(b)+MOD)%MOD
#define max(a, b) ((a)>(b) ? (a):(b))
#define min(a, b) ((a)<(b) ? (a):(b))
#define chmax(a, b) (a<b ? a=b : 0)
#define chmin(a, b) (a>b ? a=b : 0)
#define INF 1000000000000000000
#define MOD 1000000007LL
#define MAX 101010
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef map<ll, ll> Map;


int main(void) {
    ll N, K;
    cin >> N >> K;
    
    if(N>=2*K-1) {
        puts("YES");
    }else {
        puts("NO");
    }
    
    
    
    
}