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 <iostream>
#include <vector>
using namespace std;
int main(void){
    int n, k;
    cin >> n >> k;
    vector<int>c(n + 1);
    for (int i = 0; i < n; i++) {
        c[i] = n - i;
    }
    
    int ans = 0;
    for (int i = 0; i < n; i++) {
        if (c[i] - 1 != 1) ans++;
    }
    
    if (ans >= k) cout << "YES";
    else cout << "NO";
}