import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int aHP = scanner.nextInt();
        int aPower = scanner.nextInt();
        int bHP = scanner.nextInt();
        int bPower = scanner.nextInt();
        bHP -= aPower;
        while(bHP > 0) {
            aHP -= bPower;
            if (aHP < 1) {
                System.out.println("No");
                return;
            }
            bHP -= aPower;
        }
        System.out.println("Yes");
    }
}
/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