#include <iostream>
#include <string>
#include <iomanip>
#include <math.h>

using namespace std;

int main(){
	
	
	double a,b,c,d;
	cin >> a >>  b >> c >> d;
	//cout << d <<a << b <<c;
	if (b>=c){
		cout << "Yes" <<endl;
	}
	else if (d>=a){
		cout << "No"<<endl;
	}
	else{
		if (ceil(c/b)<=ceil(a/d)){ //9 11 10 10
		cout << ceil(c/b);
		cout << "Yes"<<endl;}
		else
		cout <<"No"<<endl;
	}
	
	
	
	return 0;
	
	
	
}