1 // time 32ms
2 #include <iostream>
3 #include <cstdio>
4 #include <cstring>
5 #include <cmath>
6 #include <algorithm>
7 #include <string>
8 #include <vector>
9 #include <set>
10 #include <map>
11 #include <stack>
12 #include <queue>
13 #include <sstream>
14 #include <iomanip>
15 using namespace std;
16 typedef long long LL;
17 const int INF = 0x4fffffff;
18 const double EXP = 1e-5;
19 const int MS = 1005;
20 const int SIZE = 100005;
21
22 struct edge
23 {
24 int u,v;
25 void output()
26 {
27 printf("%d---%d",u,v);
28 }
29 int cmp(edge &t)
30 {
31 return ((u==t.u&&v==t.v)||(u==t.v&&v==t.u));
32 }
33 };
34
35 edge sta[MS];
36 int top;
37 int edges[MS][MS]; // 1:连接未入stack，2：连接入过stack
38 int vis[MS];
39 int n,m;
40 int tdfn;
41 int dfn[MS];
42 int low[MS];
43
44 void DFS(int u)
45 {
46 for(int v=1;v<=n;v++)
47 {
48 if(edges[u][v]==1)
49 {
50 edge t;
51 t.u=u;t.v=v;sta[++top]=t;
52 edges[u][v]=edges[v][u]=2;
53 if(!vis[v])
54 {
55 vis[v]=1;
56 dfn[v]=low[v]=++tdfn;
57 DFS(v);
58 low[u]=min(low[u],low[v]);
59 if(low[v]>=dfn[u])
60 {
61 bool FirstEdge=true;
62 while(1)
63 {
64 if(top<0)
65 break;
66 if(FirstEdge)
67 FirstEdge=false;
68 else
69 printf(" ");
70 edge t1;
71 t1=sta[top];
72 t1.output();
73 sta[top].u=0;sta[top].v=0;//删除top边
74 top--;
75 if(t1.cmp(t))
76 break;
77 }
78 printf("\n");
79 }
80 }
81 else
82 low[u]=min(low[u],dfn[v]);
83 }
84 }
85 }
86
87
88 int main()
89 {
90 int i,u,v,number=1;
91 while(1)
92 {
93 scanf("%d%d",&n,&m);
94 if((n+m)==0)
95 break;
96 memset(edges,0,sizeof(edges));
97 for(int i=1;i<=m;i++)
98 {
99 scanf("%d%d",&u,&v);
100 edges[u][v]=edges[v][u]=1;
101 }
102 if(number++>1)
103 printf("\n");
104 low[1]=dfn[1]=1;
105 tdfn=1;
106 memset(vis,0,sizeof(vis));
107 vis[1]=1;
108 memset(sta,0,sizeof(sta));
109 top=-1;
110 DFS(1);
111 }
112 return 0;
113 }
