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factorial – Factorial of a number

Write a program that computes the factorial of a number n, or simply n!.

We can recursively define the factorial of a number as:

In symbolic terms:

By the above definition, the factorial of 4 is 24

Input and Output

Input will contain several lines with a single integer n where 0 ≤ n ≤ 12. Output should contain a line with the factorial of n.

Example input

4
6

Example output

24
720

The factorial function

Your program should contain a factorial function that takes an integer and returns an integer. Please refer to the information for your chosen language:

Specifically for this exercise when using Python, JavaScript, Lua or Ruby, avoid using sys.exit(), process.exit(), os.exit() or exit, as your program is appended with some extra assertions in one of the test sets.

Scoring

try first: good oddeven factorial1

try next: power

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