#include <iostream>
#include <iomanip>
using namespace std;
int main(void) {
	double a, b, x, y;
	cin >> a >> b >> x >> y;
	double
		c = (a + b) * x / a,
		d = (a + b) * y / b;
	cout << fixed << setprecision(10) 
		<< min(c, d) << endl;
	return 0;
}