using System;

class MainClass 
{
    public static void Main (string[] args) 
    {
        double X = double.Parse(Console.ReadLine());
        double Y = double.Parse(Console.ReadLine());
        double Z = double.Parse(Console.ReadLine());

        if(X == 0 && Z == 0)
            throw new DivideByZeroException("X and Z is zero");
        
        Console.WriteLine($"F = {Math.Pow(Math.Min(X, Math.Max(X + Y, Z)), 2) / (X * X + Z * Z)}");

    }
}