// P32 (**) Determine the greatest common divisor of two positive integer
//          numbers.
//     Use Euclid's algorithm.
//
//     scala> gcd(36, 63)
//     res0: Int = 9

object S99Int {
  def gcd(m: Int, n: Int): Int = if (n == 0) m else gcd(n, m % n)
}