import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

				Scanner sc = new Scanner(System.in);

				int T_hp = sc.nextInt();
				int T_attack = sc.nextInt();

				int A_hp = sc.nextInt();
				int A_attack = sc.nextInt();


				int A_turn = 0;
				int T_turn =1;
				//どちらかのヒットポイントが0以下になるまで繰り返す。
					while(T_hp > 0 && A_hp > 0) {
					//カウントが1のほうが攻撃を仕掛ける。
						if(T_turn ==1) {
							A_hp = A_hp - T_attack;
							A_turn = 1;
							T_turn = 0;
						}else if(A_turn == 1) {
							T_hp = T_hp - A_attack;
							T_turn = 1;
							A_turn = 0;
						}
					}
				//}
				if(T_hp > 0) {
					System.out.println("Yes");
				}else if(T_hp <= 0) {
					System.out.println("No");
				}


			}
		}

/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