Background
The greatest common divisor of two or more integers is the largest positive integer that divides each of the integers without a remainder. For example, the GCD of 8 and 12 is 4, because 4 is the largest number that divides both 8 and 12 without leaving a remainder.
Task
Define a function gcd that takes two parameters:
When called, the function should return the greatest common divisor of two integers.