input: Write a function to compute the factorial of a given number. The function should return the factorial of the given integer input. If the input is 0 or a negative number, the function should return 1.
  def factorial(n):
   if n <= 0:
    return 1
   fact = 1
   for i in range(2,n+1):
    fact = fact * i
   return fact
  assert factorial(7)==5040
  assert factorial(4)==24
  assert factorial(-3)==1
  assert factorial(0)==1
output: def factorial(n):
   if n <= 0:
    return 1
   fact = 1
   for i in range(2,n+1):
    fact = fact * i
   return fact