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#include <cstdio>
#include <string>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;
const int MAX = 1100;
char str[MAX][25];
int n, in[MAX], out[MAX];
vector<string> words[30];
int vis[30];
int f[30], ss, is, os, ps;
int seq[MAX], step;
void find_euler(int pos)
...{
int i,j;
while(out[pos]) ...{
for(; vis[pos] < words[pos].size() ;) ...{
string snext = words[pos][ vis[pos] ];
j = snext[snext.length() -1] -'a';
out[pos] --;
vis[pos] ++;
find_euler(j);
}
}
seq[step ++] = pos;
}
void union_f(int s,int e)
...{
int ts = s, te = e;
while(s != -1 && f[s] != s) ...{
s = f[s];
}
if(s == -1) ...{
f[ts] = s = ts;
}
while(e != -1 && f[e] != e) ...{
int t = e;
e = f[e];
f[t] = s;
}
if(e >= 0) ...{
f[e] = s;
}
}
int main()
...{
int t,i,j;
scanf("%d", &t);
while(t --) ...{
scanf("%d", &n);
getchar();
for(i=0;i<30;i++) words[i].clear();
memset(in,0,sizeof(in));
memset(out,0,sizeof(out));
memset(f,-1,sizeof(f));
ss = is = os = ps = 0;
for(i=0;i<n;i++) ...{
gets(str[i]);
int len = strlen(str[i]);
int chs = str[i][0] -'a';
int che = str[i][len-1] -'a';
words[chs].push_back(string(str[i]));
in[che] ++;
out[chs] ++;
union_f(chs, che);
}
bool flag = true;
for(i=0;i<30;i++) ...{
if(f[i] == i) ss ++;
if(in[i] == out[i] +1) os ++;
else if(in[i] +1 == out[i]) is ++;
else if(in[i] != out[i]) flag = false;
}
if(ss > 1) flag = false;
if( !(os==0 && is==0) && !(os==1 && is==1) ) flag = false;
if(!flag) ...{
puts("***");
}
else ...{
int spos;
if(os == 1 && is == 1) ...{
for(i=0;i<30;i++) ...{
if(in[i] +1 == out[i]) ...{
spos = i;
break;
}
}
}
else ...{
for(i=0;i<30;i++) ...{
if(f[i] != -1) ...{
spos = i;
break;
}
}
}
for(i=0;i<30;i++) sort(words[i].begin(), words[i].end());
step = 0;
memset(vis, 0, sizeof(vis));
find_euler(spos);
//memset(vis, 0, sizeof(vis));
for(i=step-1;i>0;i--) ...{
spos = seq[i];
string snext;
for(j=0;j<words[spos].size();j++) ...{
snext = words[spos][j];
if(seq[i-1] == snext[snext.length() -1] -'a') ...{
words[spos].erase(words[spos].begin() +j);
break;
}
}
printf("%s", snext.c_str());
if(i>1) putchar('.');
}
puts("");
}
}
}