#include <iostream>
#include <list>
#include <set>
#include <vector>
#include "concatenate.hpp"

int main() {
   std::vector<int> a = {1, 2, 3};
   std::list<int> b = {4, 5, 6};
   std::set<int> c = {7, 8, 9};
   for (int i: a & b & c & a) {
      std::cout << " " << i;
   }
   std::cout << std::endl;
}