#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <stdio.h>
#include <cmath>
#include <sstream>
#include <algorithm>
#include <iomanip>

#define ll long long
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define vi vector<int>
#define vl vector<long long>
#define sz size()
#define x first
#define y second
#define pii pair<int, int>
#define pll pair<ll, ll>


using namespace std;

string a[1010];
int T, n, st, ft, degin[100], degout[100], deleted[1010];
vi g[1010];
vector<pii> edges;
char ch[30];
stack<int> S;
vector<string> words[100][100];

bool euler_check() {

    for(int i = 1; i <= 26; i++) {
        if(degin[i] - degout[i] == 1) {
            if(ft == 0) ft = i;
            else return false;
        } else if(degin[i] - degout[i] == -1) {
            if(st == 0) st = i;
            else return false;
        }
    }

    if((st == 0 && ft != 0) || (st != 0 && ft == 0)) return false;

    edges.pb(mp(ft, st));
    g[ft].pb(edges.sz - 1);
    words[ft][st].pb("###");

    return true;
}

vi find_euler_path() {
    S.push(st);
    vi ans;

    while(!S.empty()) {
        int v = S.top();
        for(int i = 0; i < g[v].sz; i++) {
            int ind = g[v][i];
            int to = edges[ind].s;
            if(!deleted[ind]) {
                S.push(to);
                deleted[ind] = 1;
                break;
            }
        }

        if(v == S.top()) {
            S.pop();
            ans.pb(v);
        }
    }

    return ans;
}

void clear() {
    for(int i = 1; i <= 1000; i++) {
        g[i].clear();

    }

    for(int i = 1; i <= 26; i++) {
        degin[i] = degout[i] = 0;
        for(int j = 1; j <= 26; j++) {
            words[i][j].clear();
        }
    }

    edges.clear();
    st = ft = 0;

}

void solve(int cs) {
    clear();

    scanf("%d", &n);

    for(int i = 1; i <= n; i++) {
        scanf("%s", ch);
        a[i] = ch;
    }


    for(int i = 1; i <= n; i++) {
        edges.pb(mp(a[i][0] - 'a' + 1, a[i][a[i].sz - 1] - 'a' + 1));
        g[a[i][0] - 'a' + 1].pb(edges.sz - 1);


        degin[a[i][a[i].sz - 1] - 'a' + 1]++;
        degout[a[i][0] - 'a' + 1]++;

        words[a[i][0]][a[i][a[i].sz - 1]].pb(a[i]);
    }

    printf("Case %d: ", cs);

    if(!euler_check()) {
        printf("No\n");
        return;
    }

    vi v = find_euler_path();
    reverse(v.begin(), v.end());

    vector<string> ans;

    for(int i = 0; i < v.sz; i++) {
        cout << char(v[i] + 'a' - 1) << " ";
    }
}

int main() {
    //freopen("", "r", stdin);
    //freopen("", "w", stdout);
    scanf("%d", &T);
    for(int i = 1; i <= T; i++) {
        solve(i);
    }

    return 0;
}