1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cmath>
 5 #include <cstring>
 6 #include <algorithm>
 7 #include <queue>
 8 #include <stack>
 9 #include <vector>
10 #define MP(a, b) make_pair(a, b)
11 #define PB(a) push_back(a)
12 
13 using namespace std;
14 
15 typedef long long ll;
16 typedef pair<int ,int> pii;
17 typedef pair<unsigned int, unsigned int> puu;
18 typedef pair<int ,double> pid;
19 typedef pair<ll, int> pli;
20 
21 const int INF = 0x3f3f3f3f;
22 const double eps = 1e-6;
23 const int LEN = 1010;
24 struct Arc{
25     int from, to;
26 }bri[LEN];
27 int mp[LEN][LEN], n, nbri, low[LEN], dfn[LEN], dfs_clock, vis[LEN];
28 vector<int> Map[LEN];
29 inline bool cmp(Arc a, Arc b)
30 {
31     if(a.from != b.from) return a.from<b.from;
32     else return a.to<b.to;
33 }
34 
35 
36 //割边模版
37 //初始化
38 //for(int i=0; i<LEN; i++)Map[i].clear();
39 //memset(vis, 0, sizeof vis);
40 void dfs(int u, int fa)
41 {
42     int v, i, son = 0;
43     vis[u] = 1;
44     dfn[u] = low[u] = dfs_clock++;
45     for(int i = 0; i < Map[u].size(); i++){
46         v = Map[u][i];
47         if(vis[v] == 1 && v != fa)low[u] = min(low[u], low[v]);
48         if(vis[v] == 0){
49             dfs(v, u);
50             son++;
51             low[u] = min(low[u], low[v]);
52             if(low[v] > dfn[u])bri[nbri].from = min(u, v), bri[nbri++].to = max(v, u);
53         }
54     }
55 }
56 
57 int main()
58 {
59 //    freopen("in.txt", "r", stdin);
60 
61     int from, to, tn;
62     while(scanf("%d", &n)!=EOF)
63     {
64         memset(mp, 0 ,sizeof mp);
65         for(int i=0; i<LEN; i++)Map[i].clear();
66         memset(vis, 0, sizeof vis);
67         dfs_clock = 0, nbri = 0;
68         for(int i=0; i<n; i++){
69             scanf("%d (%d)", &from, &tn);
70             for(int j=0; j<tn; j++){
71                 scanf("%d", &to);
72                 if(!mp[from][to]){
73                     mp[from][to] = mp[to][from] = 1;
74                     Map[from].PB(to);
75                     Map[to].PB(from);
76                 }
77             }
78         }
79         for(int i=0; i<n; i++){
80             if(vis[i]==0){
81                 dfs(i, -1);
82             }
83         }
84         sort(bri, bri+nbri, cmp);
85         printf("%d critical links\n", nbri);
86         for(int i=0; i<nbri; i++) printf("%d - %d\n", bri[i].from, bri[i].to);
87         printf("\n");
88     }
89     return 0;
90 }