1 #include <cstdio>
  2 #include <cstring>
  3 #include <string>
  4 #include <iostream>
  5 #include <algorithm>
  6 #include <vector>
  7 #include <queue>
  8 #include <stack>
  9 #include <map>
 10 using namespace std;
 11 #define N 10005
 12 
 13 struct node{
 14     int x, y, id, id1, id2;
 15 }ans[N];
 16 
 17 struct mem{
 18     int y, id, id1, id2;
 19 };
 20 
 21 vector<mem>ve[N];
 22 map<string,int>ma;
 23 map<int,string>mb;
 24 int low[N], dfn[N];
 25 int visited[N];
 26 int n, m, dfn_clock;
 27 int nu;
 28 
 29 void init(){
 30     for(int i=0;i<=n;i++) ve[i].clear();
 31     ma.clear();mb.clear();
 32     memset(dfn,-1,sizeof(dfn));
 33     memset(visited,0,sizeof(visited));
 34 }
 35 
 36 void dfs(int u,int fa){
 37     int i, j, k, v;
 38     node p;
 39     mem q;
 40     //printf("1111111111\n");
 41     low[u]=dfn[u]=dfn_clock++;
 42     
 43     visited[u]=1;
 44     for(i=0;i<ve[u].size();i++){
 45         q=ve[u][i];
 46         if(q.y==fa) continue;
 47     //    printf("%d\n",v);
 48         if(!visited[q.y]){
 49             dfs(q.y,u);
 50             low[u]=min(low[u],low[q.y]);
 51             if(low[q.y]>dfn[u]) {
 52                 p.x=u;p.y=q.y;p.id=q.id;p.id1=q.id1;p.id2=q.id2;
 53                 ans[nu++]=p;
 54             }
 55         }
 56         else low[u]=min(low[u],dfn[q.y]);
 57         
 58     }
 59 }
 60 
 61 bool cmp(node a,node b){
 62     return a.id<b.id;
 63 }
 64 
 65 main()
 66 {
 67     int t, i, j, k, id;
 68     char s1[200], s2[200];
 69     mem p;
 70     cin>>t;
 71     while(t--){
 72         scanf("%d %d",&n,&m);
 73         init();k=1;id=1;
 74         while(m--){
 75             scanf("%s%s",s1,s2);
 76             if(ma[s1]==0) ma[s1]=k,mb[k]=s1,++k;
 77             if(ma[s2]==0) ma[s2]=k,mb[k]=s2,++k;
 78             int x=ma[s1], y=ma[s2];
 79             p.y=ma[s2];p.id=id++;p.id1=1;p.id2=2;
 80             ve[x].push_back(p);
 81             p.y=ma[s1];p.id=id++;p.id1=2;p.id2=1;
 82             ve[y].push_back(p);
 83         }
 84     
 85         dfn_clock=nu=0;
 86          dfs(1,-1);
 87          int f=1;
 88         for(i=1;i<=n;i++) {
 89             if(dfn[i]==-1){
 90             break;
 91             }
 92         }
 93         if(i<=n){
 94             printf("0\n");continue;
 95         }
 96         sort(ans,ans+nu,cmp);
 97         printf("%d\n",nu);
 98         for(i=0;i<nu;i++){
 99             if(ans[i].id1<ans[i].id2)
100             cout<<mb[ans[i].x]<<" "<<mb[ans[i].y]<<endl;
101             else cout<<mb[ans[i].y]<<" "<<mb[ans[i].x]<<endl;
102         }
103     }
104 }