#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int N = 1e5 + 1;
int n, m;
vector<int> adj[N];
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rand(int x) { return uniform_int_distribution<int>(0, x - 1)(rng); }
int d[N];
bool inq[N];
bool vis3[N];
bool ok = true;
void dfs3(int id) {
  inq[id] = true;
  vis3[id] = true;
  for (auto x : adj[id]) {
    if (!vis3[x]) {
      dfs3(x);
    } else if (!inq[x])
      ok = false;
  }
  inq[id] = false;
}
bool arin(int x) {
  for (int i = 1; i <= n; i++) vis3[i] = inq[i] = false;
  ok = true;
  dfs3(x);
  return ok;
}
bool vis[N];
vector<int> ch[N];
int par[N];
int dx[N], dy[N];
int cs[N];
int up[N];
void dfs(int id) {
  vis[id] = true;
  up[id] = id;
  for (auto x : adj[id]) {
    if (!vis[x]) {
      d[x] = d[id] + 1;
      par[x] = id;
      ch[id].push_back(x);
      cs[id] = x;
      dfs(x);
    } else {
      dx[x]--;
      dx[id]++;
      if (d[up[id]] > d[x]) up[id] = x;
    }
  }
  for (auto x : ch[id]) {
    if (d[up[x]] < d[up[id]]) up[id] = up[x];
  }
}
int dfs4(int id) {
  int duh = dx[id];
  for (auto x : ch[id]) duh += dfs4(x);
  dy[id] = duh;
  return duh;
}
bool good[N];
int rt;
void dfs2(int id) {
  if (dy[id] <= 1) good[id] = good[up[id]];
  if (id == rt) good[id] = true;
  for (auto x : ch[id]) {
    dfs2(x);
  }
}
void solve() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    adj[i].clear();
    ch[i].clear();
    dx[i] = dy[i] = 0;
    good[i] = false;
  }
  for (int i = 1; i <= m; i++) {
    int u, v;
    cin >> u >> v;
    adj[u].push_back(v);
  }
  int x = 0;
  for (int i = 1; i <= 100; i++) {
    x = rand(n) + 1;
    if (arin(x)) break;
    x = 0;
  }
  if (x == 0) {
    cout << "-1\n";
    return;
  }
  for (int i = 1; i <= n; i++) vis[i] = false;
  d[x] = 0;
  dfs(x);
  rt = x;
  dfs4(x);
  dfs2(x);
  int cnt = 0;
  for (int i = 1; i <= n; i++)
    if (good[i]) cnt++;
  if (cnt * 5 < n) {
    cout << "-1\n";
    return;
  }
  for (int i = 1; i <= n; i++)
    if (good[i]) cout << i << ' ';
  cout << '\n';
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t;
  cin >> t;
  while (t--) solve();
}
