Merge sort

#include<iostream>
using namespace std;
void merge(int arr[], int l, int m, int r)
{
    int i, j, k;
    int n1 = m - l + 1;
    int n2 = r - m;
    int L[n1], R[n2];
    for (i = 0; i < n1; i++) L[i] = arr[l + i];
    for (j = 0; j < n2; j++) R[j] = arr[m + 1+ j];
    i=0,j=0,k=l;
    while (i < n1 && j < n2)
    {
        if (L[i] <= R[j]) arr[k++] = L[i++];
        else
            arr[k++] = R[j++];
    }
    while (i < n1)
    {
        arr[k++] = L[i++];
    }
    while (j < n2)
    {
        arr[k++] = R[j++];
    }
}
void vengefelo(int arr[], int l, int r)
{
    if (l < r)
    {
        int m = l+(r-l)/2;
        vengefelo(arr, l, m);
        vengefelo(arr, m+1, r);
        merge(arr, l, m, r);
    }
}
void printkoro(int A[], int size)
{
    for (int i=0; i < size; i++) cout<<A[i]<<" ";cout<<endl;
}
int main()
{
    int arr[] = {12, 11, 13, 5, 6, 7};
    int arr_size = sizeof(arr)/sizeof(arr[0]);
    cout<<endl<<"ogochhalo array"<<endl;
    printkoro(arr, arr_size);
    vengefelo(arr, 0, arr_size - 1);
    cout<<"gochhano array"<<endl;
    printkoro(arr, arr_size);
    return 0;
}