Again, consider the following recurrence relation named M for mysterious: M(x, y) = M(x-y, y) if x > y //x and y are non-negative integers M(x, y) = M(x, y-x) if y > x M(x, y) = x if x = y What does this code do? (Characterized from a mathematical standpoint)

It calculates the least common divisor It calculates the average It calculates the greatest common multiple It calculates the greatest common divisor. It calculates the least common multiple It always returns 1