Problem Statement

Takahashi and Aoki will have a battle using their monsters.
The health and strength of Takahashi's monster are A and B, respectively, and those of Aoki's monster are C and D, respectively.
The two monsters will take turns attacking, in the order Takahashi's, Aoki's, Takahashi's, Aoki's, ...
Here, an attack decreases the opponent's health by the value equal to the attacker's strength.
The monsters keep attacking until the health of one monster becomes 0 or below. The person with the monster whose health becomes 0 or below loses, and the other person wins.
If Takahashi will win, print Yes; if he will lose, print No.

Input

Input is given from Standard Input in the following format:
A B C D

Output

If Takahashi will win, print Yes; if he will lose, print No.

Constraints

• $1 \leq A,B,C,D \leq 100$
• All values in input are integers.

Sample Input 1

10 9 10 10

Sample Output 1

No

First, Takahashi's monster attacks Aoki's monster, whose health is now 10-9=1.
Next, Aoki's monster attacks Takahashi's monster, whose health is now 10-10=0.
Takahashi's monster is the first to have 0 or less health, so Takahashi loses.

Sample Input 2

46 4 40 5

Sample Output 2

Yes

见题面 Input 部分

见题面 Output 部分