#include <stdio.h>
int main(void){
    int atk_a,atk_b,hp_a,hp_b;
    int i=0;
    scanf("%d",&hp_a);
    scanf("%d",&atk_a);
    scanf("%d",&hp_b);
    scanf("%d",&atk_b);

    while(hp_a>0 && hp_b>0){
        if(i%2==0){
            hp_b -= atk_a;
        }
        if(i%2==1){
            hp_a -= atk_b;
        }
        i++;
    }
    if(hp_a<=0){
        printf("No\n");
        return 0;
    }
    printf("Yes\n");
    return 0;
}
    
