input: Write a function to calculate the factorial of a given integer. If the input is less than or equal to 1, return 1. Otherwise, return the product of the number and the factorial of the number minus one. Then use this function in a program that takes an integer input from the user and prints out the factorial of that number.
  
  def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1) 
  
  assert factorial(7) == 5040
  assert factorial(0) == 1
  assert factorial(1) == 1
  assert factorial(5) == 120
  assert factorial(-10) == 1
  
  n = int(input("Enter a number: "))  
  print("Factorial of",n,"is",factorial(n))
output: def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)