(Recursive Greatest Common Divisor) The greatest common divisor of integers x and y is the largest integer that evenly divides both x and y. What is a recursive function gcd that returns the greatest common divisor of x and y, defined recursively as follows: If y is equal to 0, then gcd(x, y) is x; otherwise, gcd(x, y) is gcd(y, x % y), where % is the modulus operator. [Note: For this algorithm, x must be larger than y.]