#include <iostream>
using namespace std;

int main() {
	unsigned long long a, b, c, d; cin >> a >> b >> c >> d;
	if (b < 0) { a *= -1LL; b *= -1LL; }
	if (d < 0) { c *= -1LL; d *= -1LL; }
	if (a * d < b * c) cout << "Yes" << endl;
	else cout << "No" << endl;
	return 0;
}