#include <iostream>
#include <vector>

template <typename T>
std::ostream& operator <<(std::ostream& text, const std::vector<T>& vec) {
    if (vec.empty()) {
        return text << "[]";
    }

    auto current = vec.begin();
    auto last = --vec.end();

    text << '[';

    for (; current != last; ++current) {
        text << *current << ", ";
    }

    return text << *last << ']';
}

int main() {
    std::vector<int> vec = {1, 2, 3};

    std::cout << vec;
}