input: Write a python function to calculate the nth Fibonacci number using recursion.
  assert Fibonacci(0) == 0
  assert Fibonacci(1) == 1
  assert Fibonacci(5) == 5
  assert Fibonacci(10) == 55
  assert Fibonacci(15) == 610
output: def Fibonacci(n):
      if n <= 1:
          return n
      else:
          return Fibonacci(n-1) + Fibonacci(n-2)