#include <iostream>
#include <algorithm>
using namespace std;
int main() {
	int ah, aa, bh, ba;
	double ka, kb;
	cin >> ah >> aa >> bh >> ba;
	ka = bh / aa;
	kb = ah / ba;
	if (ceil(ka)>=ceil(kb))
	{
		cout << "Yes" << endl;
	}
	else
	{
		cout << "No" << endl;
	}
}