class combSet
{
public:
    void add(int a)
    {
        tab.push_back(a);
    }
    int calculate()
    {
        go_step(0, -1);
        return get_max();
    }
private:
    void go_step(int sum, int i)
    {
        if ( i >= (int)tab.size()-1)
        {
            sums.push_back(sum);
            std::cout << "sum= "<< sum << std::endl;
            return;
        }
        go_step(sum + tab[i+1], i+1);
        if (i < (int)tab.size()-2)
            go_step(sum + tab[i+2], i+2);
        else
            go_step(sum, i+2);
    }
    int get_max()
    {
        int xd =  tab[0];//*std::max_element(tab.begin(), tab.end());
        for (auto i = 0u; i < tab.size(); i++)
        {
            std::cout << "vec-" << tab[i] << std::endl;
            if (tab[i]>xd)
            {
                xd = tab[i];
            }
        }
        std::cout << "xd = " << xd << std::endl;
        if (tab.size() == 1)
        return 0;
        return xd;
    }
    std::vector<int> tab;
    std::vector<int> sums;a
};