#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
	bool toggle = true;
	vector<int> vec = {6, 2, 5, 3, 4, 1};
	
	vec.erase(remove_if(vec.begin(), vec.end(), [&toggle](int) { toggle = !toggle; return toggle; }), vec.end());
	
	for(auto& i: vec) {
		cout <<	i << endl;
	}
}