#include<bits/stdc++.h>
using namespace std;

#define int long long int
const int N=1e3;

int32_t main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);

	int a,b,c,d,count=0;
	cin>>a>>b>>c>>d;
	while(true){
		count++;
		if(count%2 == 0){
			a -= d;
		}
		else
			c -= b;
		if(a <= 0)
			break;
		if(c <= 0)
			break;
	}
	if(count%2 == 1)
		cout<<"Yes\n";
	else
		cout<<"No\n";

	return 0;
}