#include <bits/stdc++.h>
using namespace std;

bitset<55> b[22][55];
int T, n, m;
string s, ss;


int main(){
    cin >> T;
    while(T--) {
        cin >> n >> m;

        for(int i = 1; i <= n; ++i) {

            cin >> s;
            cin >> ss;
            for(int j = 0; j < m; ++j) {
                b[i][j].reset();
                for(int k = 0; k < m; ++k) {
                    if(ss[k] == s[j]) {
                        b[i][j][k] = 1;
                    }
                }

            }

        }
        bool vis[55];
        vector<int> ans;
        memset(vis, 0, sizeof(vis));
        for(int j = 0; j < m; ++j) {
            bitset<55> bb;
            bb.set();
            for(int i = 1; i <= n; ++i) {
                bb &= b[i][j];
            }
            for(int i = 0; i < m; ++i) {
                if(bb[i] && vis[i] == 0) {
                    vis[i] = 1;
                    ans.emplace_back(i + 1);
                    break;
                }
            }
        }
        if(ans.size() == m) {
            for(int i = 0; i < m; ++i) {
                cout << ans[i] << (i == m - 1 ? '\n' : ' ');
            }
        }
        else {
            cout << -1 << endl;
        }




    }
    return 0;
}