#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

template <typename It>
void PrintRange(It range_begin, It range_end) {
    for (auto it = range_begin; it != range_end; ++it) {
        cout << *it << " "s;
    }
    cout << endl;
}

template <typename RandomIt>
void MergeSort(RandomIt range_begin, RandomIt range_end) {
    int range_num = distance(range_begin, range_end); // количество элементов в контейнере
    if (range_num < 2) return;
    auto mid = range_begin + (range_end - range_begin) / 2; // середина контейнера

    MergeSort(range_begin, mid);
    MergeSort(mid + 1, range_end);
    merge(range_begin, mid, mid+1, range_end, greater<>());
}

int main() {
    vector<int> a, b;
    a = { 5,4,3,2,1 };
    b = { 4,3,2,1 };

    random_shuffle(a.begin(), a.end());
    PrintRange(a.begin(), a.end());
    MergeSort(a.begin(), a.end());
    PrintRange(a.begin(), a.end());

    /*PrintRange(b.begin(), b.end());
    MergeSort(b.begin(), b.end());
    PrintRange(b.begin(), b.end());*/
}