Merging k sorted lists (Merge 2 at a time)

import java.io.*;
import java.util.*;

public class Main {

    static int n, k;
    static int[] arr, aux;

    // from arr[lo] to arr[mid] is sorted
    // from arr[mid+1] to arr[hi] is sorted
    // at the end of the procedure: from arr[lo] to arr[hi] is sorted
    static void merge(int lo, int mid, int hi) {     // O(n) where n = hi-lo+1
        for (int k = lo; k <= hi; k++) {
            aux[k] = arr[k];
        }

        int i = lo, j = mid + 1;
        for (int k = lo; k <= hi; k++) {
            if (i > mid)
                arr[k] = aux[j++];
            else if (j > hi)
                arr[k] = aux[i++];
            else if (aux[j] < aux[i])
                arr[k] = aux[j++];
            else
                arr[k] = aux[i++];
        }
    }

    public static void main(String args[]) {

        Scanner read = new Scanner(System.in);
        n = read.nextInt();     // total number of elements
        k = read.nextInt();     // number of lists
        arr = new int[n];
        aux = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = read.nextInt();
        }

        // Step 1: Merge arrays (1 and 2), arrays (3 and 4), and so on.
        // Step 2: Merge array (1,2 and 3,4), arrays (5,6 and 7,8), and so on
        // Step 3: Repeat...
        // sz is number of elements per list = n/k
        // important note: each step, sz will be doubled, sz = sz*2
        // assume n = 8, k = 4
        //          0  1   2  3   4  5   6  7
        // arr[] = {3, 4,  1, 2,  7, 8,  5, 6}
        //         <(1)>   <(2)>  <(3)>  <(4)>
        // Step 1: Merge arrays (1 and 2)
        //              merge(lo = 0, hi = 3, mid = 1)
        //         Merge arrays (3 and 4)
        //              merge(lo = 4, hi = 7, mid = 5)
        // Step 2: Merge array (1,2 and 3,4)
        //              merge(lo = 0, hi = 7, mid = 3)
        // we can  think of the parameters as the following with the help of sz important note
        // Step 1 (sz= n/k = 8/4 = 2):
        //         Merge arrays (1 and 2)
        //              merge(lo = 0, hi = lo + (2*sz) - 1 = 3, mid = lo+sz-1 = 1)
        //         Merge arrays (3 and 4)
        //              merge(lo = 4, hi = lo + (2*sz) - 1 = 7, mid = lo+sz-1 = 5)
        // Step 2 (sz = sz*2 = 4): : Merge array (1,2 and 3,4)
        //              merge(lo = 0, hi = lo + (2*sz) - 1 = 7, mid = lo+sz-1 = 3)
        // the remaining is: lo = ?
        for (int sz = n / k; sz < n; sz = sz * 2) {
            for (int lo = 0; lo < n - sz; lo += sz * 2) {
                int hi = lo + (2 * sz) - 1;
                int mid = lo + sz - 1;
                merge(lo, mid, hi);
            }
        }


        for (int i = 0; i < n; i++) {
            System.out.print(arr[i] + " ");
        }

    }

}