Recursive Factorial Calculation in Python

# Introduction

In mathematics, the 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, `5! = 5 x 4 x 3 x 2 x 1 = 120`. In this challenge, you will write a Python function to calculate the factorial of a given number using recursion.