Write a C ++ program to implement Merge Sort algorithm to efficiently handle an input array that may contain duplicate elements. The goal is to modify the algorithm in such a way that duplicate elements appear in the sorted array in the same order as they appear in the input.

#include <iostream>

using namespace std;

void merge(int a[], int low, int mid, int high)
{
	int i = low;
	int j = mid + 1;
	int k = low;
	int temp[20];

	while(i <= mid && j <= high)
	{
		if(a[i] <= a[j])
		{
			temp[k] = a[i];
			k++;
			i++;
		}
		else
		{
			temp[k] = a[j];
			k++;
			j++;
		}
	}

	while(i <= mid)
	{
		temp[k] = a[i];
		k++;
		i++;
	}

	while(j <= high)
	{
		temp[k] = a[j];
		k++;
		j++;
	}

	for(i = low; i < k