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

#define GO ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define int long long int

const int maxr = 1e5 + 5;


int32_t main()
{
	GO;
	int a, b, c, d;
	cin >> a >> b >> c >> d;
	bool turn = 0;
	while (a > 0 && c > 0) {
		if (turn) {
			a -= d;
		}
		else {
			c -= b;
		}
		turn ^= 1;
	}
	if (a <= 0)
		cout << "No" << endl;
	else
		cout << "Yes" << endl;
	return 0;
}

//!