#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <map>
using namespace std;

vector<int> count(string s)
{
    vector<int> res(26);
    for (int i = 0; i < s.size(); ++i) {
        res[s[i] - 'a'] += 1;
    }
    return res;
}

vector<long long> cand(string s)
{
    vector<long long> res(26);
    for (int i = 0; i < s.size(); ++i) {
        res[s[i] - 'a'] |= 1LL<<i;
    }
    return res;
}

void process()
{
    int N, M;
    cin >> N >> M;

    string q, r;

    vector<long long> valid(M, (1LL<<M) - 1);

    bool fail = false;
    for (int i = 0; i < N; ++i) {
        cin >> q;
        cin >> r;

        if (count(q) != count(r)) {
            fail = true;
            continue;
        }

        vector<long long> cc = cand(r);
        for (int j = 0; j < M; ++j) {
            valid[j] &= cc[q[j]-'a'];
        }
    }

    if (fail) {
        cout << -1 << endl;
        return;
    }

    vector<bool> used(M, false);

    vector<int> res;
    for (int i = 0; i < M; ++i) {
        for (int j = 0; j < M; ++j) {
            if (((valid[i] >> j)&1) && !used[j]) {
                res.push_back(j + 1);
                used[j] = true;
                break;
            }
        }
    }

    if (res.size() < M) {
        cout << -1 << endl;
        return;
    }

    cout << res[0];
    for (int i = 1; i < M; ++i) {
        cout << ' ' << res[i];
    }
    cout << endl;
}

int main(void)
{
    int T;
    cin >> T;
    for (int i = 1; i <= T; ++i)
    {
        process();
    }
    return 0;
}