#include <cassert>
#include <deque>
#include <iostream>

int main() {
    std::deque<int> jobs{10, 20, 30};
    int* middle = &jobs[1];
    jobs.push_front(5);
    jobs.push_back(40);
    assert(*middle == 20 && middle == &jobs[2]);

    auto keep = jobs.begin() + 2;
    jobs.pop_front();
    assert(*keep == 20);
    assert(keep == jobs.begin() + 1);
    jobs.pop_back();
    assert(*keep == 20);
    assert((jobs == std::deque<int>{10, 20, 30}));
    std::cout << jobs.front() << ' ' << *keep << ' ' << jobs.back() << '\n';
}