#include <vector>
#include <iostream>

using namespace std;

class List
{
    public:
        typedef vector<int>::iterator iterator;
        typedef vector<int>::const_iterator const_iterator;

        iterator begin() { return arr.begin(); }
        iterator end() { return arr.end(); }
        const_iterator begin() const { return arr.cbegin(); }
        const_iterator end() const { return arr.cend(); }

        void add(int n) { arr.push_back(n); }
    private:
        vector<int> arr;
};

int main()
{
    List m;
    m.add(1);
    m.add(2);
    m.add(3);

    for(int i : m) {
        cout << i << endl;
    }
    return 0;
}