#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>

int main(void){

    int t_hp, t_atk, a_hp, a_atk;

    scanf("%d", &t_hp);
    scanf("%d", &t_atk);
    scanf("%d", &a_hp);
    scanf("%d", &a_atk);

    // printf("%d\n", t_hp);
    // printf("%d\n", t_atk);
    // printf("%d\n", a_hp);
    // printf("%d\n", a_atk);

    while(1){

        a_hp = a_hp - t_atk;
        if(a_hp <= 0){
            printf("Yes\n");

            break;
        }
 
        t_hp -= a_atk;
        if(t_hp <= 0){
            printf("No\n");

            break;
        }



    }

    return 0;
}