using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var p = int.Parse(line[0]);
        var q = int.Parse(line[1]);
        var r = int.Parse(line[2]);
        var t = Max(p + q, Max(q + r, r + p));
        Console.WriteLine((double)t / (p + q + r));
    }
}