#include <vector>
#include <unordered_set>
#include <iterator>
#include <iostream>

using namespace std;

int main() {
    vector<int> destination = {1, 2, 3, 4, 5};
    unordered_set<int> source = {11111, 22222, 33333, 44444, 55555};

    back_insert_iterator<vector<int>> bi(destination);
    // auto bi = back_inserter(destination);

    copy(source.begin(), source.end(), bi);

    for (auto v : destination)
	  cout << v << ' ';
    cout << '\n';
}