#include <bits/stdc++.h>
using namespace std;
const int inf = (int)1.01e9;
const long long infll = (long long)1.01e18;
const long double eps = 1e-9;
const long double pi = acos((long double)-1);
mt19937 mrand(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x) { return mrand() % x; }
void precalc() {}
const int maxn = (int)1e5 + 5;
int n, m;
vector<int> g[maxn];
bool read() {
  if (scanf("%d%d", &n, &m) < 2) {
    return false;
  }
  for (int i = 0; i < n; i++) {
    g[i].clear();
  }
  for (int i = 0; i < m; i++) {
    int v, u;
    scanf("%d%d", &v, &u);
    v--;
    u--;
    g[v].push_back(u);
  }
  return true;
}
int used[maxn];
int tin[maxn], tout[maxn], t;
void dfs0(int v) {
  used[v] = true;
  tin[v] = t++;
  for (int i = 0; i < ((int)(g[v]).size()); i++) {
    int u = g[v][i];
    if (!used[u]) {
      dfs0(u);
    }
  }
  tout[v] = t;
}
bool anc(int v, int u) { return tin[v] <= tin[u] && tout[u] <= tout[v]; }
int incnt[maxn];
int cnt[maxn], tov[maxn];
int go[maxn];
bool dfs1(int v) {
  used[v] = true;
  cnt[v] = 0;
  tov[v] = v;
  for (int i = 0; i < ((int)(g[v]).size()); i++) {
    int u = g[v][i];
    if (used[u]) {
      if (!anc(u, v)) {
        return false;
      }
      incnt[u]++;
      cnt[v]++;
      if (anc(u, tov[v])) {
        tov[v] = u;
      }
    } else {
      if (!dfs1(u)) {
        return false;
      }
      cnt[v] += cnt[u];
      if (anc(tov[u], tov[v])) {
        tov[v] = tov[u];
      }
    }
  }
  cnt[v] -= incnt[v];
  go[v] = (cnt[v] == 1 ? tov[v] : -1);
  return true;
}
int good[maxn];
void dfs2(int v) {
  used[v] = true;
  if (go[v] == v) {
    good[v] = true;
  } else if (go[v] == -1) {
    good[v] = false;
  } else {
    good[v] = good[go[v]];
  }
  for (int i = 0; i < ((int)(g[v]).size()); i++) {
    int u = g[v][i];
    if (!used[u]) {
      dfs2(u);
    }
  }
}
vector<int> ans;
bool solve1(int s) {
  for (int i = 0; i < n; i++) {
    used[i] = false;
  }
  t = 0;
  dfs0(s);
  for (int i = 0; i < n; i++) {
    used[i] = false;
    incnt[i] = 0;
  }
  if (!dfs1(s)) {
    return false;
  }
  for (int i = 0; i < n; i++) {
    used[i] = false;
  }
  go[s] = s;
  dfs2(s);
  ans.clear();
  for (int i = 0; i < n; i++) {
    if (good[i]) {
      ans.push_back(i);
    }
  }
  if (((int)(ans).size()) * 5 < n) {
    printf("-1\n");
  } else {
    for (int i = 0; i < ((int)(ans).size()); i++) {
      printf("%d ", ans[i] + 1);
    }
    printf("\n");
  }
  return true;
}
const int K = 70;
void solve() {
  for (int it = 0; it < K; it++) {
    int s = rnd(n);
    if (solve1(s)) {
      return;
    }
  }
  printf("-1\n");
}
int main() {
  precalc();
  int t;
  scanf("%d", &t);
  while (read()) {
    solve();
  }
  return 0;
}
