Factorial Calculator

Welcome to the Factorial Factorium! 🎉

In this challenge, you're going to build a magic factorial calculator! 🧙‍♂️

A factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example:

• 0! = 1 (by definition)
• 1! = 1
• 2! = 2 × 1 = 2
• 3! = 3 × 2 × 1 = 6
• 4! = 4 × 3 × 2 × 1 = 24

Your mission, should you choose to accept it, is to implement a function that calculates the factorial of a given number n.

Examples:

factorial(0)  # returns 1
factorial(1)  # returns 1
factorial(3)  # returns 6
factorial(5)  # returns 120

Let's start coding and unveil the magic of factorials! 🌟