import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int tt = sc.nextInt();
        int tk = sc.nextInt();
        int at = sc.nextInt();
        int ak = sc.nextInt();
        while(true) {
            at -= tk;
            if(at <= 0) {
                System.out.println("Yes");
                return;
            }
            tt -= ak;
            if(tt <= 0) {
                System.out.println("No");
                return;
            }
        }
    }
}
/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