input: Write a function to understand the concept of recursion in Python. The function should calculate the factorial of a given number using recursion. If the number is 1, return 1; otherwise, return the product of the number and the factorial of the number minus one.
  def factorial(n):
     if n == 1:
        return 1
     else:
        return n * factorial(n - 1)
  assert factorial(5)==120
  assert factorial(3)==6
  assert factorial(1)==1
  assert factorial(4)==24
  assert factorial(6)==720
output: def factorial(n):
     if n == 1:
        return 1
     else:
        return n * factorial(n - 1)