import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.StringTokenizer;

public class Main {

static int N;

static int count;

static int[] arr;

static boolean[] visited;

public static void main(String[] args) throws NumberFormatException, IOException {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

N = Integer.parseInt(br.readLine());

count = 2*N-1;

arr = new int[count];

visited = new boolean[count];

StringTokenizer token = new StringTokenizer(br.readLine());

for (int i=0; i