#include <bits/stdc++.h>
#define PI 3.14159265359
using namespace std;

int main() {
	double A, B, X, Y;
	cin >> A >> B >> X >> Y;

	double n, m;
	n = (double)A / B;
	m = (double)X / Y;

	if (n > m) {
		Y = (double)B * (X / A);
	}
	else if (n < m) {
		X = (double)A * (Y / B);
	}

	double sum = (double)X + Y;
	cout << fixed << setprecision(10) << sum << endl;
}