#include<stdio.h>
int main(void) {
	int atk1, health1, atk2, health2,i;
	scanf("%d %d %d %d", &health1, &atk1, &health2, &atk2);
	i = 0;
	while ((health1 > 0) && (health2 > 0)) {
		if (i % 2 == 0) {
			health2 -= atk1;
		}
		else {
			health1 -=atk2;
		}
		i += 1;
		} 
	if (i % 2 == 0) {
		printf("No");
	}
	else {
		printf("Yes");
	}
	return 0;
}