#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;

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

	ll l, r, m, k;;
	cin >> l >> r >> m >> k;

	ll lk = l * k,
		rk = r * k;

	ll lkw = (lk / m) * m;

	string res{ "No" };
	if (lkw == lk || lkw + m <= rk) 
		res = "Yes";
	cout << res << "\n";

	return 0;
}