std::deque::operator[]

#include <deque>
#include <iostream>

int main()
{
    std::deque<int> numbers {2, 4, 6, 8};

    std::cout << "Second element: " << numbers[1] << '\n';

    numbers[0] = 5;

    std::cout << "All numbers:";
    for (auto i : numbers) {
        std::cout << ' ' << i;
    }
    std::cout << '\n';
}