input: Write a function to generate the nth Fibonacci number using a recursive approach. Return 1 for the 1st and 2nd Fibonacci numbers, and for any other number, return the sum of the two preceding 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)