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>
#include <vector>
using namespace std;

void mergeWithoutRepetition(vector<int>& v, int start, int middle, int end) {
	vector<int> left(v.begin() + start, v.begin() + middle + 1);
	vector<int> right(v.begin() + middle + 1, v.begin() + end + 1);
  
	int i = 0, j = 0, k = start;
	while(i < left.size() && j < right.size()) {
		if(left[i] <= right[j]) {
			v[k++] = left[i++];
		} else {
			v[k++] = right[j++];
		}
	}
  
	while(i < left.size()) {
		v[k++] = left[i++];
	}
	while(j < right.size()) {
		v[k++] = right[j++];
	}
}