import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int tHP = sc.nextInt();
        int tAtack = sc.nextInt();
        int aHP = sc.nextInt();
        int aAtack = sc.nextInt();
        boolean isTkhsWin = false;

        while(true) {
            // 高橋の攻撃
            aHP -= tAtack;
            if (aHP <= 0) {
                isTkhsWin = true;
                break;
            }
            // 青木の攻撃
            tHP -= aAtack;
            if (tHP <= 0) {
                isTkhsWin = false;
                break;
            }
        }
        String result = isTkhsWin ? "Yes" : "No";
        System.out.println(result);
    }
}
/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