#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <string>
#include <tuple>
#include <functional>
#include <numeric>
#include <cmath>
#include <iomanip>
#include <map>
#include <random>
//#include "toollib.h"
#define INT_MAX 2147483647
#define Loop(i, n) for(int i = 0; i < (int)n; i++)
#pragma warning (disable:4018)

using namespace std;
typedef long long int lint;

//***** Main Program *****

int main() {
	int A, B, X, Y;
	cin >> A >> B >> X >> Y;
	double ret;
	if (X*B <= Y*A) {
		ret = (double)X*(A + B) / A;
	}
	else {
		ret = (double)Y*(A + B) / B;
	}
	cout << setprecision(12) << ret << endl;
}