#include <cassert>
#include <memory>
#include <stdexcept>

struct Ticket {
    static int alive;
    Ticket() { ++alive; }
    ~Ticket() noexcept { --alive; }
    Ticket(const Ticket&) = delete;
    Ticket& operator=(const Ticket&) = delete;
};
int Ticket::alive = 0;

std::unique_ptr<Ticket> make_ticket(bool valid) {
    auto result = std::make_unique<Ticket>();
    if (!valid) throw std::invalid_argument("invalid ticket");
    return result;
}

int main() {
    bool caught = false;
    try { auto ticket = make_ticket(false); }
    catch (const std::invalid_argument&) { caught = true; }
    assert(caught && Ticket::alive == 0);
    {
        auto ticket = make_ticket(true);
        assert(Ticket::alive == 1);
    }
    assert(Ticket::alive == 0);
}