#include <vector>
#include <iostream>

class Stack
{

public:

    Stack& operator<<(int value)
    {
        values.push_back(value);
        return *this;
    }

    Stack& operator>>(int& value)
    {
        value = values.back();
        values.pop_back();
        return *this;
    }

    unsigned int size() const
    {
        return values.size();
    }
    
    std::string to_string() const
    {
        std::string result { };
        for (size_t i { values.size() }; i > 0; --i)
        {
            result += std::to_string(values[i - 1]) + " ";
        }
        result.pop_back();
        return result;
    }
    
private:

    std::vector<int> values {};
    
};

int main()
{
    Stack st { };

    st << 3 << 2 << 1;
    std::cout << st.to_string()<< std::endl;

    while (st.size() > 0)
    {
        int value;
        st >> value;
        std::cout << value << " ";
    }
    std::cout << std::endl;
}