#include <stdio.h>
#include <stdint.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}

int main() {
	int l = ri();
	int r = ri();
	int m = ri();
	int k = ri();
	int64_t min = (int64_t) l * k;
	int64_t max = (int64_t) r * k;
	if (min % m) min -= min % m, min += m;
	puts(min <= max ? "Yes" : "No");
	return 0;
}