final class WalkDistance(val x: Int) extends AnyVal {
    def get: Int = x
    def isEmpty = x < 3000
  }

final class CarDistance(val x: Int) extends AnyVal {
    def get: Int = x / 1000
    def isEmpty = x >= 3000
  }

def select(distance: Int) = distance match{
    case WalkDistance(w) => s"I will walk ${w} meters}
    case CarDistance(c) => s"I will drive ${x} km}
}