1 #include<algorithm>
2 #include<iostream>
3 #include<cstring>
4 #include<string>
5 #include<cstdio>
6 #include<vector>
7 #include<stack>
8 using namespace std;
9 struct node
10 {
11 int w,num;
12 };
13 vector<node>v[27];
14 stack<int>stk;
15 int n,f[27],ru[1001],chu[1001];
16 string s[1001];
17 bool b[1001];
18 int fnd(int x)
19 {
20 return f[x]==x?x:f[x]=fnd(f[x]);
21 }
22 void fluery(int u,int eid)
23 {
24 for(int i=0;i<v[u].size();i++)
25 if(!b[v[u][i].num])
26 {
27 b[v[u][i].num]=1;
28 fluery(v[u][i].w,v[u][i].num);
29 }
30 if(eid>0)
31 stk.push(eid);
32 }
33 int main()
34 {
35 int t;
36 scanf("%d",&t);
37 while(t--)
38 {
39 memset(ru,0,sizeof(ru));
40 memset(chu,0,sizeof(chu));
41 for(int i=1;i<=26;i++)
42 v[i].clear();
43 scanf("%d",&n);
44 for(int i=1;i<=n;i++)
45 cin>>s[i];
46 sort(s+1,s+n+1);
47 for(int i=1;i<=26;i++)
48 f[i]=i;
49 int p;
50 for(int i=1;i<=n;i++)
51 {
52 int x=s[i][0]-'a'+1,y=s[i][s[i].length()-1]-'a'+1;
53 chu[x]++;
54 ru[y]++;
55 node tmp;
56 tmp.w=y;
57 tmp.num=i;
58 v[x].push_back(tmp);
59 if(i==1)
60 p=x;
61 f[fnd(y)]=fnd(x);
62 }
63 bool flg=0;
64 int fa=fnd(p);
65 for(int i=1;i<=26;i++)
66 {
67 if(!ru[i]&&!chu[i])
68 continue;
69 if(fnd(i)!=fa)
70 {
71 flg=1;
72 break;
73 }
74 }
75 if(flg)
76 {
77 printf("***\n");
78 continue;
79 }
80 int st=-1,en=-1,tot=0;
81 for(int i=1;i<=26;i++)
82 {
83 if(!ru[i]&&!chu[i])
84 continue;
85 if(ru[i]!=chu[i])
86 tot++;
87 if(ru[i]==chu[i]-1)
88 st=i;
89 if(ru[i]==chu[i]+1)
90 en=i;
91 }
92 if(tot&&(tot!=2||en<0||st<0))
93 printf("***\n");
94 else
95 {
96 if(tot==0)
97 st=p;
98 memset(b,0,sizeof(b));
99 fluery(st,0);
100 while(!stk.empty())
101 {
102 int tmp=stk.top();
103 stk.pop();
104 cout<<s[tmp];
105 if(!stk.empty())
106 printf(".");
107 }
108 printf("\n");
109 }
110 }
111 return 0;
112 }
113
