#include <atomic>
#include <mutex>
class Counter {
private:
    std::atomic<int> counter_;
    twist::mutex mtx_;
    twist::conditional_variable cv_is_zero_;
public:
    explicit Counter(int init_value = 0) : counter_(init_value) {};

    void Increment() {
        auto locker = twist::LockUnique(mtx_);
        counter_.fetch_add(1);
        cv_is_zero_.notify_one(mtx_);
    }

    void Decrement() {
        auto locker = twist::LockUnique(mtx_);
        counter_.fetch_add(-1);
        cv_is_zero_.notify_one(mtx_);
    }

    void AwaitZero() {
        auto locker = twist::LockUnique(mtx_);
        while (!counter_ == 0) {
            cv_is_zero_.wait(locker);
        }
    }
};