using System;
using System.Collections.Generic;
using System.Linq;

namespace No236
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			var line = Console.ReadLine ().Split (' ').Select (v => Convert.ToInt32 (v)).ToArray ();
			double a = line [0];
			double b = line [1];
			double x = line [2];
			double y = line [3];
			var ax = a / x;
			var by = b / y;
			if (ax > by) {
				var r = x + x / a * b;
				Console.WriteLine (r.ToString ());
				return;
			} else {
				var r = y + y / b * a;
				Console.WriteLine (r.ToString ());
				return;
			}

		}
	}
}