import java.util.ArrayList;
import java.util.Scanner;
import java.util.TreeMap;

public class Solution {
    private String[] arr = new String[10];

    public static void main(String[] args) {
        new Solution().run();
    }

    private void run() {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        TreeMap<String, ArrayList<String>> mp = new TreeMap<String, ArrayList<String>>();

        for (int i = 0; i < n - 1; ++i) {
            String s1 = sc.next();
            String s2 = sc.next();
            if (mp.containsKey(s2)) {
                mp.get(s2).add(s1);
            } else {
                ArrayList<String> tmp = new ArrayList<String>();
                tmp.add(s1);
                mp.put(s2, tmp);
            }
        }
        write(mp, "main", 0);

    }

    private void write(TreeMap<String, ArrayList<String>> mp, String str, int offset) {
        for (int i = 0; i < offset; ++i) {
            System.out.print(" ");
        }
        System.out.println(str);

        if (mp.containsKey(str)) {
            for (int i = 0; i < mp.get(str).size(); ++i) {
                String tmp = mp.get(str).get(i);
                write(mp, tmp, offset + 2);
            }
        }
    }
}