using System;

public class Test
{
	public static void Main()
	{
		Console.WriteLine(FractionToDouble("4 1/5"));
	}
    
    private static double FractionToDouble(string fraction) {
        double result;
    
        if(double.TryParse(fraction, out result)) {
            return result;
        }
    
        string[] split = fraction.Split(new char[] { ' ', '/' });
    
        if(split.Length == 2 || split.Length == 3) {
            int a, b;
    
            if(int.TryParse(split[0], out a) && int.TryParse(split[1], out b)) {
                if(split.Length == 2) {
                    return (double)a / b;
                }
    
                int c;
    
                if(int.TryParse(split[2], out c)) {
                    return a + (double)b / c;
                }
            }
        }
    
        throw new FormatException("Not a valid fraction.");
    }
}