func_code_string: #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;   }   