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

int main() {
	int ta, thp, aa, ahp,tn,an;
	scanf("%d %d %d %d", &thp, &ta, &ahp, &aa);
	tn = ahp / ta;
	an = thp / aa;
	if (ahp%ta != 0) {
		tn = tn + 1;
	}
	if (thp%aa != 0) {
		an = an + 1;
	}
	if (an < tn) {
		printf("No");
	}
	else {
		printf("Yes");
	}
}