// реализация функции mapreduce
template<typename It, typename UnFunc, typename BiFunc>
auto map_reduce(It p, It q, UnFunc f1, BiFunc f2, size_t threads)->decltype(f2(f1(*p), f1(*p)))
{
    using ResType = decltype(f2(f1(*p), f1(*p)));
    size_t block_size = std::distance(p, q) / threads;

    std::vector<It> first(threads);
    std::vector<It> last(threads);
    int c = 0;
    for (int i = 0; i < threads; i++)
    {
        first[i] = p;
        while (c < (i+1)*block_size)
        {
            last[i] = ++p;
            c++;
        }
    }
    last[threads-1] = q;

    std::vector <ResType> VectResult(threads);
    for (int i = 0; i < threads; i++)
    {
        ResType res;
        std::thread t([&res]() {res = map<It, UnFunc, BiFunc>(p, q, f1, f2);});
        t.join();
        VectResult[i] = res;
    }

    /*std::vector<std::future<ResType>> VectFuture(threads);


    for (int i = 0; i < threads; i++)
    {
        VectFuture[i] = std::async(std::launch::async, map <It, UnFunc, BiFunc>, first[i], last[i], f1, f2);
    }
    ResType res = VectFuture[0].get();
    for (int i = 1; i < threads; i++)
    {
        res = f2(res, VectFuture[i].get());
    }*/

    return res;
}