#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
#define all(x) (x).begin(), (x).end()
#define fsp(x) fixed << setprecision(x)
//const ll p = 1e9 + 7;
//const ll p = 998244353;
const ll inf = LLONG_MAX;
const long double pi = acos(-1);
void Yes() {cout << "Yes" << endl;}
void No() {cout << "No" << endl;}
void YES() {cout << "YES" << endl;}
void NO() {cout << "NO" << endl;}

int main() {
	//ios::sync_with_stdio(false);
	//cin.tie(nullptr);

	ll a, b, c, d;
	cin >> a >> b >> c >> d;
	while (a > 0 && c > 0) {
		c -= b;
		if (c <= 0) {
			Yes();
			return 0;
		}
		a -= d;
		if (a <= 0) {
			No();
			return 0;
		}
	}
}
