# Exercise: The Factorial!

Let's create a function that calculates the factorial of a number.

## We'll cover the following

## Problem Statement #

In this challenge, you must implement the `factorial()`

function. It takes an integer as a parameter and calculates its factorial. Python does have a built-in factorial function but you’ll be creating your own for practice.

The factorial of a number,

n, is its product with all the integers between0andn.

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