#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp> // Общий файл.
//#include <ext/pb_ds/tree_policy.hpp> // Содержит класс tree_order_statistics_node_update

#define ll long long
#define ull unsigned long long
#define ld long double
#define len(v) (int)v.size()
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pii pair<int, int>
#define vi vector<int>
#define vii vector<vector<int>>
#define vpii vector<pair<int, int>>
#define dcout cout << setprecision(7)
#define mkp make_pair
#define EL '\n'
//#define int long long
//#define ll ull
const int maxn = 1e5 + 10;
const int C = 20;
const int logn = 20;
const int inf = 1e9;
const ll mod = 1073741824;
//const int M = 1e9;
const ll M = 998244353;
const int m1 = (1 << 16), m2 = (1 << 30);
const ld eps = 1e-9;
using namespace std;
//using namespace __gnu_pbds;

//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
//ordered_set s;

// random
std::mt19937_64 gen(std::chrono::steady_clock::now().time_since_epoch().count());

template<class T>
istream &operator>>(istream &in, vector<T> &a) {
    for (auto &i : a)
        in >> i;
    return in;
}

template<class T>
ostream &operator<<(ostream &out, vector<T> &a) {
    for (auto &i : a)
        out << i << ' ';
    return out;
}

ifstream fin("a2.txt");
ofstream fout("aboba.txt");

int n;
vector<string> a;
multiset<string> b;
bool used[maxn * 2];
vector<int> uind;

bool isans = false;
void rec(string up, int cnt = 0) {
    if (up == "AA" && cnt == n && uind[0] == 3) {
        cout << "";
    }
    if (cnt == n) {
        // check & output

        vector<string> ans(n);
        ans[0] = up;
        for (int i = 1; i < n; ++i) {
            for (int k : uind) {
                ans[i] += a[k][i];
            }
        }
        multiset<string> c = b;
        for (auto& s : ans) {
            if (c.find(s) == c.end()) return;
            c.erase(c.find(s));
        }
        for (int k : uind) {
            if (c.find(a[k]) == c.end()) return;
            c.erase(c.find(a[k]));
        }
        if (c.empty()) {
            for (auto &s: ans)
                cout << s << EL;
            cout << EL;
            isans = true;
        }
        return;
    }
    for (int i = cnt; i < n; ++i) {
        char c = up[i];
        for (int j = 0; j < n * 2; ++j) {
            if (!used[j] && c == a[j][0]) {
                used[j] = true;
                uind.push_back(j);
                if (isans) return;
                rec(up, cnt + 1);
                uind.pop_back();
                used[j] = false;
            }
        }
    }
}

void solve() {
    cin >> n;
    a.resize(n * 2); cin >> a;
    for (auto& s : a)
        b.insert(s);
    for (int i = 0; i < n * 2 && !isans; ++i) {
        used[i] = true;
        rec(a[i]);
        used[i] = false;
    }
    isans = false;
    a.clear();
    b.clear();
    uind.clear();
    for (bool& i : used)
        i = false;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int T = 1;
    cin >> T;
    while (T--) {
        //fout << 2;
        solve();
    }
}