#include <bits/stdc++.h>
using namespace std;
int main(){
	int A, B, C, D, E, F;
	cin >> A >> B >> C >> D;
	E = (A - A % D) / D;
	F = (C - C & B) / B - 1;
	if(E < F){
		cout << "Yes";
    }else{
		cout << "No";
    }
}