#include <cstdio>
#include <iostream>


struct Item
{
    Item *next;
    long long value;
};

class Arena {
public:
    Arena(const Arena&) = delete;
    Arena &operator=(Arena other) = delete;

    Item *arr = nullptr;
    bool *arr_vacant = nullptr;
    size_t newsize = 0;

    explicit Arena(size_t size) {
        newsize = size / sizeof(Item);
        if (newsize) {
            Item *arr = new Item[newsize];
            bool *arr_vacant = new bool[newsize];

            for (size_t i = 0; i < newsize; ++i) {
                arr_vacant[i] = false;
            }
        }
    }

    ~Arena() {
        delete[] arr;
        delete[] arr_vacant;
    }

    Item *get() {
        for (size_t i = 0; i < newsize; ++i) {
            if (arr_vacant[i] == false) {
                arr_vacant[i] = true;
                return arr + i;
            }
        }
        return nullptr;
    }


    void put(Item *it) {
        for (size_t i = 0; i < newsize; ++i) {
            if (arr + i == it) {
                arr_vacant[i] = false;
            }
        }
    }


};


// int main()
// {
//     Arena t(200);
// }