// yuki 1048 Zero (Advanced)
// 2021.8.12

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

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

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