input: Write a function to generate Fibonacci numbers recursively. The function should take an integer n as input and return the nth Fibonacci number. If n is less than or equal to 0, return 0, and if n is 1 or 2, return 1.
  def fibonacci(n):
      if n <= 0:
          return 0
      elif n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)
  assert fibonacci(10) == 55
  assert fibonacci(1) == 1
  assert fibonacci(2) == 1
  assert fibonacci(0) == 0
  assert fibonacci(-5) == 0
output: def fibonacci(n):
      if n <= 0:
          return 0
      elif n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)