package com.company;
import java.util.*;
import java.lang.*;
import java.math.*;

public class Boot {
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);

        int linesCount = Integer.parseInt(scan.nextLine());
        int[] firstArr = new int[linesCount];
        int[] secondArr = new int[linesCount];
        for (int i = 0; i < linesCount; i++)
        {
            int[] numbers = Arrays.stream(scan.nextLine().split(" "))
                    .mapToInt(e -> Integer.parseInt(e)).toArray();

            if (i % 2 == 0)
            {
                firstArr[i] = numbers[0];
                secondArr[i] = numbers[1];
            }
            else
            {
                firstArr[i] = numbers[1];
                secondArr[i] = numbers[0];
            }
        }
        System.out.print(firstArr + " ");
        System.out.print(secondArr + " ");
    }
}