#include <bits/stdc++.h>
#pragma GCC optimize("Ofast", "unroll-loops", "no-stack-protector")
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using uint = unsigned int;
using ull = unsigned long long;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
default_random_engine generator;
void solve();
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << setprecision(16) << fixed;
  cerr << setprecision(16) << fixed;
  int tests = 1;
  cin >> tests;
  for (int test = 1; test <= tests; ++test) {
    solve();
  }
}
const int MAXN = 100100;
vector<int> g[MAXN];
int used[MAXN];
bool dfs(int v) {
  used[v] = 1;
  for (int u : g[v]) {
    if (used[u] == 2) {
      return false;
    } else if (!used[u] && !dfs(u)) {
      return false;
    }
  }
  used[v] = 2;
  return true;
}
int good[MAXN];
int up[MAXN][2];
int tin[MAXN];
int timer = 0;
int f[MAXN];
void update(int v, int x) {
  if (x == 0 || tin[v] == x) {
    return;
  }
  if (up[v][0] == 0 || up[v][0] > x) {
    up[v][1] = up[v][0];
    up[v][0] = x;
  } else if (up[v][1] == 0 || up[v][1] > x) {
    up[v][1] = x;
  }
}
void dfs1(int v) {
  used[v] = 1;
  tin[v] = ++timer;
  f[tin[v]] = v;
  for (int u : g[v]) {
    if (!used[u]) {
      dfs1(u);
      update(v, up[u][0]);
      update(v, up[u][1]);
    } else {
      update(v, tin[u]);
    }
  }
}
void dfs2(int v) {
  used[v] = 1;
  good[v] = true;
  if (up[v][1] != 0 || up[v][0] == 0) {
    good[v] = false;
  } else {
    good[v] = good[f[up[v][0]]];
  }
  for (int u : g[v]) {
    if (!used[u]) {
      dfs2(u);
    }
  }
}
void solve() {
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < n; ++i) {
    g[i].clear();
  }
  for (int i = 0; i < m; ++i) {
    int u, v;
    cin >> u >> v;
    --u;
    --v;
    g[u].push_back(v);
  }
  int root = -1;
  for (int t = 0; t < 100; ++t) {
    memset(used, 0, sizeof(int) * n);
    int v = rnd() % n;
    if (dfs(v)) {
      root = v;
      break;
    }
  }
  if (root == -1) {
    cout << "-1\n";
    return;
  }
  timer = 0;
  memset(used, 0, sizeof(int) * n);
  memset(up, 0, sizeof(up[0]) * n);
  dfs1(root);
  up[root][0] = tin[root];
  memset(used, 0, sizeof(int) * n);
  memset(good, 0, sizeof(int) * n);
  dfs2(root);
  vector<int> res;
  for (int i = 0; i < n; ++i) {
    if (good[i]) {
      res.push_back(i);
    }
  }
  if ((int)(res).size() * 5 >= n) {
    for (int v : res) {
      cout << v + 1 << " ";
    }
    cout << "\n";
  } else {
    cout << "-1\n";
  }
}
