input: Write a function to compute the factorial of a given number. The function should take an integer as input and return the factorial of that number. If the input number is 0 or 1, the function should return 1.
  def factorial(n):
   fact = 1
   for i in range(2,n+1):
    fact = fact * i
   return fact
  assert factorial(7)==5040
  assert factorial(0)==1
  assert factorial(1)==1
  assert factorial(5)==120
  assert factorial(4)==24
output: def factorial(n):
   fact = 1
   for i in range(2,n+1):
    fact = fact * i
   return fact