import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int healthA = sc.nextInt();
        int attackB = sc.nextInt();
        int healthC = sc.nextInt();
        int attackD = sc.nextInt();
        
        boolean isTakahashiWin;
        while(true){
            healthC -= attackB;
            if(healthC <= 0){
                isTakahashiWin = true;
                break;
            }
            healthA -= attackD;
            if(healthA <= 0){
                isTakahashiWin = false;
                break;
            }
        }
        System.out.println(isTakahashiWin == true ? "Yes" : "No");
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz