#define _GLIBCXX_DEBUG
#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <deque>
#include <queue>
#include <array>
#include <set>
#include <map>
#include <cmath>
#include <algorithm>
#include <numeric>
#include <utility>
#include <tuple>
#include <functional>
#include <bitset>
#include <cstdint>
#include <cassert>
#include <random>
using namespace std;
int		cnt;

int		main(void)
{
	int A,B,C,D;
	cin >> A >> B >> C >> D;
	for (int i = 0; ; i++)
	{
		C -= B;
		if (C <= 0)
		{
			cout << "Yes" << endl;
			break ;
		}
		A -= D;
		if (A <= 0)
		{
			cout << "No" << endl;
			break ;
		}
	}

}
