Fabio is a math AI who can calculate the factorial of any number. The Rule for factorials is as follows:

Factorial (0) = 1

Factorial (1) = 1

Factorial(n) = n * n-1 * n-2 * . * 1

Write a function int Fabio (int n) to do Fabios job. The function should take one integer value, calculate its factorial using the rules above as well as loops, and return the result as an integer. If the user passes an invalid number (n