#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<utility>
#include <functional>
#include <set>
#include <map>
#include <queue>
#include <cmath>
#include <stack>

using namespace std;

int main() {
	int a, b, c, d;
	cin >> a >> b >> c >> d;
	int ha;
	int hb;
	if (a % d == 0)ha = a / d;
	else ha = a / d + 1;
	if (c % b == 0)hb = c / b;
	else hb = c/b + 1;
	if (ha >= hb)cout << "Yes";
	else cout << "No";
}