#include <bits/stdc++.h>
using namespace std;
const int MX = 100005;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n, m, x[MX], y[MX], lvl[MX], q[MX], vis[MX], res[MX], anc[MX], cn;
vector<int> adj[MX];
void clear() {
  for (int i = 1; i <= n; i++) adj[i].clear();
  iota(q, q + n, 1);
  shuffle(q, q + n, rng);
}
void add(int u, int k) {
  if (x[u] > k) {
    y[u] = x[u];
    x[u] = k;
  } else if (y[u] > k) {
    y[u] = k;
  }
}
bool dfs(int u) {
  cn++;
  vis[u] = 1;
  x[u] = y[u] = MX;
  for (int v : adj[u]) {
    if (vis[v] == 2) return 0;
    if (vis[v]) {
      add(u, lvl[v]);
      continue;
    }
    lvl[v] = lvl[u] + 1;
    if (!dfs(v)) return 0;
    add(u, x[v]);
    add(u, y[v]);
  }
  if (x[u] == lvl[u]) x[u] = MX;
  if (y[u] == lvl[u]) y[u] = MX;
  if (y[u] < MX) res[u] = 0;
  vis[u] = 2;
  return 1;
}
void dfs2(int u) {
  vis[u] = 1;
  anc[lvl[u]] = u;
  if (res[u] == -1 && lvl[u]) {
    if (x[u] < MX)
      res[u] = res[anc[x[u]]];
    else
      res[u] = 0;
  }
  for (int v : adj[u])
    if (!vis[v]) dfs2(v);
}
void solve() {
  cin >> n >> m;
  clear();
  while (m--) {
    int u, v;
    cin >> u >> v;
    adj[u].push_back(v);
  }
  for (int i = 0; i < min(n, 80); i++) {
    for (int j = 0; j < n; j++) vis[j + 1] = 0, res[j + 1] = -1;
    lvl[q[i]] = 0;
    cn = 0;
    if (!dfs(q[i]) || cn < n) continue;
    res[q[i]] = 1;
    for (int j = 0; j < n; j++) vis[j + 1] = 0;
    dfs2(q[i]);
    vector<int> r;
    for (int j = 1; j <= n; j++)
      if (res[j] == 1) r.push_back(j);
    if (5 * r.size() < n)
      cout << -1 << '\n';
    else {
      for (int x : r) cout << x << " ";
      cout << '\n';
    }
    return;
  }
  cout << -1 << '\n';
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int t;
  cin >> t;
  while (t--) solve();
  return 0;
}
