// yuki 1048 Zero (Advanced)
// 2021.8.12

#include <stdio.h>
typedef long long ll;

int main()
{
	int L, R, M, K, ans = 0;
	ll s, t;

	scanf("%d%d%d%d", &L, &R, &M, &K);
	if (L == 0) ans = 1;
	else {
		s = (ll)L*K, t = (ll)R*K;
		if (s % M == 0 || t % M == 0) ans = 1;
		else ans = (s/M != t/M);
	}
	puts(ans? "Yes": "No");
	return 0;
}