Merge sort

#include <iostream>
using namespace std;

void sherry()
{
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#endif
}

void merg(int arr[], int l, int m, int r)
{
    int i, j, k = l;
    int n1 = m - l + 1, n2 = r - m;
    int L[n1], R[n2];
    for (int i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (int i = 0; i < n2; i++)
        R[i] = arr[m + i + 1];
    i = j = 0;
    while (i < n1 and j < n2)
    {
        if (L[i] < R[j])
        {
            arr[k] = L[i];
            i++;
        }
        else
        {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
    while (i < n1)
    {
        arr[k] = L[i];
        i++, k++;
    }
    while (j < n2)
    {
        arr[k] = R[j];
        j++, k++;
    }
}
void mergeSort(int arr[], int l, int r)
{
    if (l < r)
    {
        int m = (l + r) / 2;
        mergeSort(arr, l, m);
        mergeSort(arr, m + 1, r);
        merg(arr, l, m, r);
    }
}
int main()
{
    sherry();
    ll n;
    cin >> n;
    int arr[n];
    for (int i = 0; i < n; i++)
    {
        cin >> arr[i];
    }
    mergeSort(arr, 0, n - 1);
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    return 0;
}