input: Write a function to generate Fibonacci numbers using recursion. The function should return the nth Fibonacci number. If n is 1 or 2, return 1 directly. For other values of n, return the sum of the previous two Fibonacci numbers.
  
  def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)
  
  assert fibonacci(1) == 1
  assert fibonacci(2) == 1
  assert fibonacci(10) == 55
  assert fibonacci(15) == 610
  assert fibonacci(20) == 6765
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)