#include <iostream>
#include <set>
#include <vector>
#include <algorithm>
 
using std::cout;
using std::endl;
 
using std::set;
using std::vector;
using std::remove_copy_if;
 
int main(){
	vector<int> a = {1, 2, 3, 4, 6, 5, 2, 3, 4, 1, 2, 5, 1, 3, 6, 5};
	vector<int> b(a.size());
	set<int> s;
 
	remove_copy_if(a.begin(), a.end(), b.begin(), [&](int v){
		if(s.find(v) != s.end()){
			return true;
		}else{
			s.insert(v);
			return false;
		}
	});
	b.resize(s.size());
 
	for_each(b.begin(), b.end(), [](int v){
		cout << v << ' ';
	});
 
	cout << endl;
 
	return 0;
}

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