#include <utility>

template <typename Iter>
void insert_sort(Iter first, Iter last) {
    if (first >= last) return;

    auto head = first + 1;
    while (head < last) {
        auto cursor = head;
        while (cursor > first) {
            if (*cursor < *(cursor - 1)) {
                std::swap(*cursor, *(cursor - 1));
            }
            else {
                break;
            }
            --cursor;
        }
        ++head;
    }
}

template <typename Iter>
void isort(Iter first, Iter last) {
    if (first >= last) return;

    auto length = std::distance(first, last);
    if (length < 32) {
        insert_sort(first, last);
        return;
    }

    auto left = first;
    auto right = last - 1;
    auto index = first;

    while (left < right) {
        while (*right >= *index && left < right) --right;
        if (left >= right) break;
        std::swap(*index, *right);
        index = right;

        while (*left <= *index && left < right) ++left;
        if (left >= right) break;
        std::swap(*index, *left);
        index = left;
    }

    isort(first, index);
    isort(index + 1, last);
}