$/*$

$*$ greatestCommonDenominator

$*$ Purpose: determine the largest integer that divides x and y

$*$ Parameters: int x$,$ int y

$*$ Returns: int the largest integer that divides x and y

$*$ Pre$-$conditions: x$,$ y $>0$

$*/$

$//$ TODO: write the greatestCommonDenominator method here