Recursive Factorial

Given a non-negative integer \( n \), compute its factorial using recursion. The factorial is defined as follows:

\( n! = n \times (n-1)! \) for \( n > 0 \) and \( 0! = 1 \).

If \( n \) is a negative integer, output "None".

This problem tests your understanding of recursion and edge-case handling.

inputFormat

Input is provided via standard input (stdin) as a single integer ( n ). There will be no additional characters or spaces.

outputFormat

Output via standard output (stdout): If ( n ) is non-negative, output its factorial. Otherwise, output the string "None".## sample

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