#include <iostream>
#include <list>

using namespace std;

template <typename T>
class Set {

    list<T> set;

public:
    Set() {}

    Set(T t) {
        set.insert(t);
    }

    ~Set() {
        set.clear();
    }

    void insert(T t) {
        if (!search(t)) {
            set.push_back(t);
        }
    }

    bool search(T t) {
        for (auto i = set.begin(); i != set.end(); ++i) {
            if ((*i) == t) {
                return true;
            }
        }
        return false;
    }

    Set unite(Set s) {
        Set newSet;
        newSet.set.merge(this->set);
        newSet.set.merge(s.set);
        newSet.set.unique();
        return newSet;
    }

    Set intersection(Set s) {
        Set newSet;
        for (auto i = s.set.begin(); i != s.set.end(); ++i) {
            if (this->search(*i)) {
                newSet.insert(*i);
            }
        }
        return newSet;
    }

    Set difference(Set s) {
        Set newSet;
        for (auto i = set.begin(); i != set.end(); ++i) {
            if (!s.search(*i)) {
                newSet.insert(*i);
            }
        }
        return newSet;
    }

    bool include(Set s) {
        for (auto i = s.set.begin(); i != s.set.end(); ++i) {
            if (!this->search(*i)) {
                return false;
            }
        }
        return true;
    }

    void print() {
        for (auto i = set.begin(); i != set.end(); ++i) {
            cout << *i << " ";
        }
        cout << endl;
    }

private:
};

int main() {

    return 0;
}