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 1 or 2, the function should return 1. Otherwise, the function should return the sum of the (n-1)th and (n-2)th Fibonacci numbers.
  assert fibonacci(1)==1
  assert fibonacci(2)==1
  assert fibonacci(3)==2
  assert fibonacci(4)==3
  assert fibonacci(10)==55
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)