#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#ifdef TEST
#define getchar_unlocked _getchar_nolock
#endif
#define int long long
#define ins insert
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define pf push_front
#define pp pop
#define ppb pop_back
#define ppf pop_front
#define eb emplace_back
#define g0(a) get<0>(a)
#define g1(a) get<1>(a)
#define g2(a) get<2>(a)
#define g3(a) get<3>(a)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef long double ld;
typedef long long ll;
typedef tree<pair<int, int>, null_type, less<pair<int, int> >, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int a, b, c, d;
	cin >> a >> b >>  c >> d;
	for (int i = 1; ; i++) {
		if (i & 1) {
			c -= b;
			if (c <= 0) return cout << "Yes\n", 0;
		} else {
			a -= d;
			if (a <= 0) return cout << "No\n", 0;
		}
	}
}
