#include <vector>
#include <iostream>

using namespace std;
vector<int> FindPair(vector<int> arr,int n,vector<int>& answer);

vector<int> solution(vector<int> arr)
{
    vector<int> answer;
    FindPair(arr,0,answer);
    return answer;
}

vector<int> FindPair(vector<int> arr,int n,vector<int>& answer)
{
    if(n + 1 < arr.size())
    {
        if(arr.at(n) != arr.at(n + 1))
            answer.push_back(arr.at(n));
        
        FindPair(arr,n + 1,answer);
    }
    
    if(n + 1 == arr.size())
        answer.push_back(arr.at(n));
    
    return answer;
}


효율성 빵점맞음 시발ㅋㅋ