input: Write a function to calculate the factorial of a given integer and print the result. The function should return the factorial value. If the input is less than or equal to 1, the function should return 1.
  def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1) 
  
  n = int(input("Enter a number: "))  
  print("Factorial of",n,"is",factorial(n))
  
  assert factorial(5)==120
  assert factorial(0)==1
  assert factorial(1)==1
  assert factorial(3)==6
  assert factorial(7)==5040
output: def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)