#include <bits/stdc++.h>
using namespace std;
const int c = 200002;
int w, n, m, st[c], be[c], ki[c], f[c], visz[c], visz2[c], cbe, cki, db;
vector<int> sz[c], s[c];
bool v[c], jo;
void dfs(int a) {
  v[a] = true, be[a] = cbe, cbe++;
  int v1 = a, v2 = a;
  for (int i = 0; i < sz[a].size(); i++) {
    int x = sz[a][i];
    if (!v[x]) {
      f[x] = a, dfs(x);
      if (be[visz[x]] < be[v2]) v2 = visz[x];
      if (be[v2] < be[v1]) swap(v1, v2);
      if (be[visz2[x]] < be[v2]) v2 = visz2[x];
    } else if (be[x] < be[v2])
      v2 = x;
    if (be[v2] < be[v1]) swap(v1, v2);
  }
  if (be[v2] < be[a]) st[a] = 2;
  visz[a] = v1, visz2[a] = v2;
  ki[a] = cki, cki++;
}
void dfs2(int a) {
  for (int i = 0; i < s[a].size(); i++) {
    int x = s[a][i];
    st[x] = st[a], dfs2(x);
  }
}
int vel() {
  long long a = rand(), b = rand(), c = rand();
  return (a * b + c) % n + 1;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> w;
  while (w--) {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) sz[i].clear(), s[i].clear(), st[i] = 0;
    db = 0, jo = 0;
    for (int i = 1; i <= m; i++) {
      int a, b;
      cin >> a >> b;
      sz[a].push_back(b);
    }
    for (int i = 1; i <= 10; i++) {
      if (!jo) {
        int p = vel(), r = 0;
        f[p] = 0;
        for (int i = 1; i <= n; i++) v[i] = 0, st[i] = 0;
        cbe = 1, cki = 1;
        dfs(p);
        for (int i = 1; i <= n; i++)
          for (int j = 0; j < sz[i].size(); j++) {
            int x = sz[i][j];
            if (f[x] != i && (be[i] < be[x] || ki[i] > ki[x])) r = 1;
          }
        if (!r) {
          st[p] = 1, jo = true;
          for (int i = 1; i <= n; i++)
            if (!st[i]) s[visz[i]].push_back(i);
          for (int i = 1; i <= n; i++)
            if (st[i]) dfs2(i);
        }
      }
    }
    for (int i = 1; i <= n; i++)
      if (st[i] == 1) db++;
    if (db * 5 < n)
      cout << -1;
    else
      for (int i = 1; i <= n; i++)
        if (st[i] == 1) cout << i << " ";
    cout << "\n";
  }
  return 0;
}
