using System;
using System.Linq;

class Program
{
    static void Main()
    {
        double[] d = Console.ReadLine().Split().Select(double.Parse).ToArray();
        double a = d[0];
        double b = d[1];
        double x = d[2];
        double y = d[3];

        double ans = 0;

        if (a * y > b * x) ans = x * (a + b) / a;
        else ans = y * (a + b) / b;

        Console.WriteLine(ans);
    }
}