#include <iostream>

using namespace std;

int main() {
  int a, b, x, y;
  cin >> a >> b >> x >> y;

  if ( a * y > b * x ) {
	cout << x * 1.0 * (a + b) / a << endl;
  } else {
	cout << y * 1.0 * (a + b) / b << endl;
  }
}