#include <bits/stdc++.h>

using namespace std;

#define pii pair<int, int>
#define x first
#define y second
#define ll long long

const int N = 55;
pii num[N * N]; int cnt1;
pii s[N * N];
int n, ton[N][4];
ll has[N]; 
int ton2[N][4];
ll has2[N];
map<ll, vector<int> > mp;
bool vis[N]; int f[N], ff[N];
bool fl;

int str_to_id(char ch) {
    if (ch >= 'a' && ch <= 'z') return ch - 'a';
    else return ch - 'A' + 26;
}

char id_to_str(int id) {
    if (id < 26) return 'a' + id;
    else return 'A' + id - 26; 
}

bool cmp(pii a, pii b) {
    int anum = f[a.y] + ((a.x == -1) ? 0 : f[a.x]) * n;
    int bnum = f[b.y] + ((b.x == -1) ? 0 : f[b.x]) * n;
    return anum < bnum;
}

bool check() {
    // for (int i = 0; i < n; ++i) printf("%d ", f[i]); putchar('\n');
    sort(s + 1, s + n * n + 1, cmp);
    for (int i = 1; i <= n * n; ++i){
        // printf("num[%d] = {%d, %d}, s[%d] = {%d, %d}; \n", i, num[i].x, num[i].y, i, s[i].x, s[i].y);
        if (num[i].x == -1) {
            if (s[i].x != -1 || num[i].y != f[s[i].y]) return false;
        } else {
            if (num[i].x != f[s[i].x] || num[i].y != f[s[i].y]) return false;
        }
    }
    return true;
}

void print() {
    for (int i = 0; i < n; ++i) ff[f[i]] = i;
    for (int i = 0; i < n; ++i) printf("%c", id_to_str(ff[i])); putchar('\n');
}

void dfs(int step) {
    if (fl) return;
    if (step == n) {
        if (check()) {
            print();
            fl = 1;
        }
        return;
    }
    for (auto x : mp[has2[step]]) {
        if (vis[x]) continue;
        vis[x] = 1;
        f[step] = x;
        dfs(step + 1);
        vis[x] = 0;
    }
}

void work() {
    scanf("%d", &n);
    for (int i = 0; i < n; ++i)
        for (int j = 0; j < n; ++j) {
            int v = i * j;
            num[++cnt1].y = v % n;
            num[cnt1].x = v / n;
            if (!num[cnt1].x) {
                num[cnt1].x = -1;
                ++ton[num[cnt1].y][0];
            } else {
                if (num[cnt1].x == num[cnt1].y) ++ton[num[cnt1].x][3];
                else ++ton[num[cnt1].x][1], ++ton[num[cnt1].y][2];
            }
        }
    sort(num + 1, num + n * n + 1);
    for (int i = 0; i < n; ++i) {
        ll now = 1;
        for (int j = 0; j < 4; ++j) {
            has[i] += now * ton[i][j];
            now *= n * n + 1;
        }
        mp[has[i]].push_back(i);
        // printf("has[%d] = %lld; \n", i, has[i]);
    }
    for (int i = 1; i <= n * n; ++i) {
        char str[4]; scanf("%s", str + 1);
        int len = strlen(str + 1);
        if (len == 1) {
            s[i].x = -1, s[i].y = str_to_id(str[1]);
            ++ton2[s[i].y][0];
        }
        else {
            s[i].x = str_to_id(str[1]), s[i].y = str_to_id(str[2]);
            if (s[i].x == s[i].y) ++ton2[s[i].x][3];
            else ++ton2[s[i].x][1], ++ton2[s[i].y][2];
        }
    }
    for (int i = 0; i < n; ++i) {
        ll now = 1;
        for (int j = 0; j < 4; ++j) {
            has2[i] += now * ton2[i][j];
            now *= n * n + 1;
        }
        // printf("has2[%d] = %lld; \n", i, has2[i]);
    }
    dfs(0);
    if (!fl) puts("sb");
    cnt1 = 0;
    for (int i = 0; i < n; ++i) {
        has[i] = has2[i] = 0;
        for (int j = 0; j < 4; ++j) ton[i][j] = ton2[i][j] = 0;
    } mp.clear();
    for (int i = 0; i < n; ++i) vis[i] = 0;
    fl = 0;
}

int main() {
    int Tt; scanf("%d", &Tt);
    while (Tt--) work();
}