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