#include <iostream>
using namespace std;

long long A, B, C, D;

int sgn(long long x) {
	if (x > 0) return 1;
	if (x == 0) return 0;
	return -1;
}

int main() {
	cin >> A >> B >> C >> D;
	if (sgn(B) == sgn(D)) {
		if (A * D < B * C) cout << "Yes" << endl;
		else cout << "No" << endl;
	}
	if (sgn(B) != sgn(D)) {
		if (A * D > B * C) cout << "Yes" << endl;
		else cout << "No" << endl;
	}
	return 0;
}