-

using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

class Driver {
	static Task<int> One ()
	{
		return Task<int>.Factory.StartNew (() => { return 1; });
	}


	static async Task <int> Fib (int x)
	{
		if (x <= 1)
			return await One ();
		else
			return await Fib (x - 1) + await Fib (x - 2);
	}

	static void Main () {
		var res = Fib (27);
		Console.WriteLine (res.Result);
	}
}
/*
To AOT:
From: mcs/class/lib/net_4_5
MONO_PATH=. ~/src/mono/mono/mini/mono --aot mscorlib.dll
To decompile: 
MONO_PATH=. monodis mscorlib.dll

*/