#include<bits/stdc++.h>
#define ff first
#define ss second
#define len(x) (int)(x.size())
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using ii = pair<int, int>;

int main(){
	ios::sync_with_stdio(0);
	int h1, s1, h2, s2;
	cin >> h1 >> s1 >> h2 >> s2;
	bool flag = true;
	while(h1>0 and h2>0){
		if(!flag) h1-=s2;
		else h2-=s1;
		flag = !flag;
	}
	if(h1>0)
		cout << "Yes" << endl;
	else
		cout << "No" << endl;
}
