import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt(),b = sc.nextInt(),c = sc.nextInt(),d = sc.nextInt(),z = 0;
        while(true){
            c -= b;
            a -= d;
            if(c <= 0) {
                System.out.println("Yes");
                System.exit(0);
            }if(a <= 0){
                System.out.println("No");
                System.exit(0);
            }
        }
    }
}

/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