struct Ticket: Equatable, Comparable {
    let number: Int
    static func < (left: Ticket, right: Ticket) -> Bool { left.number < right.number }
}

@main
struct Lesson {
    static func main() {
        let values = [Ticket(number: 42), Ticket(number: 18), Ticket(number: 31)]
        print(values.sorted().map { $0.number })
        print(Ticket(number: 18) == Ticket(number: 18))
    }
}