/*
* @author - Rahul Goswami
* 15 Apr, 2018
*/
#include<bits/stdc++.h>
using namespace std;
#define N 10

vector<int> adj[N];
int max_distance, farthest_node;
int parents[N];

// find farthest node
int DFS(int source, int parent, int distance) {
    if (distance > max_distance) {
        max_distance = distance;
        farthest_node = source;
    }
    for (int child: adj[source]) {
        if (child != parent)
            DFS(child, source, distance + 1);
    }
    return farthest_node;
}

// calculate array parents[N]
void dfs(int source, int parent) {
    parents[source] = parent;
    for (int child: adj[source])
        if (child != parent)
            dfs(child, source);
}

int main()
{
    freopen("input.txt", "r", stdin);
    int a, b, node_a, node_b, temp;

    for (int i=0; i<N-1; i++) {
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    max_distance = -1;
    node_a = DFS(1, -1, 0);

    max_distance = -1;
    node_b = DFS(node_a, -1, 0);

    dfs(node_a, -1);

    unordered_set<int> diameter_set;

    diameter_set.insert(node_b);
    temp = node_b;
    while (temp != node_a) {
        diameter_set.insert(parents[temp]);
        temp = parents[temp];
    }

    unordered_set<int> external_nodes;
    for (int node=0; node<N; ++node) {
        if (diameter_set.count(node) == 0)
            external_nodes.insert(node);
    }

    cout << "Minimum number of external nodes are: " << external_nodes.size();
    cout << "\nset 'external_nodes' contains these nodes:\n";
    for (int node: external_nodes)
        cout << node << " ";
    cout << "\nset 'diameter_set' contains these nodes:\n";
    for (int node: diameter_set)
        cout << node << " ";
    cout << "\n";

    return 0;
}