% 5.3	Write an iterative function called factorial that consumes a number
% and returns the factorial of the given number. The factorial of a number
% can be found using the following equation:  
%               F(x) = x*(x-1)*(x-2)…*2*1
% Remember the factorial of 0 is equal to 1, and you must protect yourself
% from negative numbers. Call the function error(…) if this occurs.
clear
clc
% Examples:
factorial(5) % -> 120
factorial(0) % -> 1
factorial(10)% -> 3628800