# gcd_r(a, b): greatest common divisor (recursive part)
define gcd_r
  {
  if ($2 == 0)
    return $1
  return gcd_r($2, $1 % $2)
}

# gcd(a, b): greatest common divisor
define gcd
  {
  a = $1 + 0
  b = $2 + 0
  if (a < 1)
    a = -a
  if (b < 1)
    b = -b
  if (a == 0 || b == 0)
    return 0
  return gcd_r(a, b)
  }