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;
typedef pair<int,int> pii;
#define dd(x) cout<<#x<<" = "<<x<<","
#define de(x) cout<<#x<<" = "<<x<<endl
#define rep(i,l,r) for(int i = l;i < r;i++)
#define per(i,l,r) for(int i = r-1;i >= l;i--)
#define pb push_back
#define mp make_pair
#define fi first
#define se second

const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
const int N = 1e6+7;
const int M = 1e6+7;
const int MOD = 1e9+7;
int dp[N][6][6];
int a[N];
int main() {
	int n,k;scanf("%d%d",&n,&k);
	if(k > (n + 1) / 2) printf("NO\n");
	else printf("YES\n");
	return 0;
}