input: Write a function to generate Fibonacci numbers using a recursive approach. The function should return the nth Fibonacci number. If n is 1 or 2, the function should return 1, otherwise it should recursively call itself to calculate the value.
  assert fibonacci(10)==55
  assert fibonacci(1)==1
  assert fibonacci(2)==1
  assert fibonacci(5)==5
  assert fibonacci(7)==13
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)