Problem:
Score : 900 points

Problem Statement

Takahashi has an ability to generate a tree using a permutation (p_1,p_2,...,p_n) of (1,2,...,n), in the following process:

First, prepare Vertex 1, Vertex 2, ..., Vertex N.
For each i=1,2,...,n, perform the following operation:

If p_i = 1, do nothing.

If p_i \neq 1, let j' be the largest j such that p_j < p_i. Span an edge between Vertex i and Vertex j'.

Takahashi is trying to make his favorite tree with this ability.
His favorite tree has n vertices from Vertex 1 through Vertex n, and its i-th edge connects Vertex v_i and w_i.
Determine if he can make a tree isomorphic to his favorite tree by using a proper permutation.
If he can do so, find the lexicographically smallest such permutation.

Notes

For the definition of isomorphism of trees, see wikipedia. Intuitively, two trees are isomorphic when they are the "same" if we disregard the indices of their vertices.

Constraints

2 \leq n \leq 10^5

1 \leq v_i, w_i \leq n

The given graph is a tree.

Input

Input is given from Standard Input in the following format:

n
v_1 w_1
v_2 w_2
:
v_{n-1} w_{n-1}

Output

If there is no permutation that can generate a tree isomorphic to Takahashi's favorite tree, print -1.
If it exists, print the lexicographically smallest such permutation, with spaces in between.

Sample Input 1

6
1 2
1 3
1 4
1 5
5 6

Sample Output 1

1 2 4 5 3 6

If the permutation (1, 2, 4, 5, 3, 6) is used to generate a tree, it looks as follows:

This is isomorphic to the given graph.

Sample Input 2

6
1 2
2 3
3 4
1 5
5 6

Sample Output 2

1 2 3 4 5 6

Sample Input 3

15
1 2
1 3
2 4
2 5
3 6
3 7
4 8
4 9
5 10
5 11
6 12
6 13
7 14
7 15

Sample Output 3

-1

Solution in Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)


import java.util.*;
import java.io.*;

public class Main {
    static ArrayList<Integer>[]adj;
    static boolean is;
    static int dfs(int u,int p) {
        int ret = 1;
        for (int v : adj[u])
            if (v != p) {
                ret += dfs(v, u);
            }
        return ret;
    }
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        int n = sc.nextInt();
        adj= new ArrayList[n];
        for (int i =0;i<n;i++)
            adj[i]=new ArrayList<>();
        for (int i =0;i<n-1;i++){
            int u = sc.nextInt()-1;
            int v = sc.nextInt()-1;
            adj[u].add(v);
            adj[v].add(u);
        }
        int grtr=0;
        int node=0;
        for (int i =0;i<n;i++){
            if (adj[i].size()>2){
                grtr++;
                node=i;
            }
        }
        if (grtr>1){
            pw.println(-1);
        }
        else if (grtr==0){
            for (int i =1;i<=n;i++)
                pw.print(i+" ");
            pw.println();
        }
        else {
            grtr=0;
            int nxt=adj[node].get(0);
            for (int v:adj[node]){
                if (adj[v].size()>1){
                    grtr++;
                    nxt=v;
                }
            }
            if (grtr>1){
                pw.println(-1);
            }
            else {
                int sz=dfs(nxt,node);
                int[]ans = new int[n];
                for (int i =0;i<sz;i++)
                    ans[i]=i+1;
                int root=sz+1;
                for (int i =sz;i<n-2;i++){
                    ans[i]=i+2;
                }
                ans[n-2]=root;
                ans[n-1]=n;
                for (int x:ans)
                    pw.print(x+" ");
                pw.println();
            }
        }
        pw.close();

    }
    static class Scanner {
        BufferedReader br;
        StringTokenizer st;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        public double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }

        public int[] nextIntArr(int n) throws IOException {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = Integer.parseInt(next());
            }
            return arr;
        }

    }

}