import java.util.*;

class Main {
    public static void main(final String[] args) {
        final Scanner scan = new Scanner(System.in);
        int a = scan.nextInt(); // Takahasi HP
        final int b = scan.nextInt();
        int c = scan.nextInt(); // Aoki HP
        final int d = scan.nextInt();
        scan. close();
        
        while(true){
            c -= b;
            if(c <= 0){
                System.out.print("Yes"); 
                break;
            }
            a -= d;
            if(a <= 0){
                System.out.println("No");
                break;
            }
        }
    }
}
/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