input: Write a function to compute the factorial of a given number. The function should return the factorial value for a non-negative integer. If the input is 0, the function should return 1.
  def factorial(n):
      if n == 0:
          return 1
      fact = 1
      for i in range(2, n + 1):
          fact *= i
      return fact
  
  assert factorial(7) == 5040
  assert factorial(0) == 1
  assert factorial(5) == 120
  assert factorial(10) == 3628800
output: def factorial(n):
      if n == 0:
          return 1
      fact = 1
      for i in range(2, n + 1):
          fact *= i
      return fact