func_code_string: #include <bits/stdc++.h>   using namespace std;   void fast() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);   }   void ran() { srand(chrono::steady_clock::now().time_since_epoch().count()); }   long long get_rand() {     long long a = rand();     long long b = rand();     return a * (RAND_MAX + 1ll) + b;   }   void solve() {     int n, m;     cin >> n >> m;     vector<int> subs[n + 1], inc[n + 1];     int labels[n + 1];     for (int i = 0; i < m; i++) {       int a, b;       cin >> a >> b;       subs[a].push_back(b);       inc[b].push_back(a);     }     vector<int> rem;     for (int i = 1; i <= n; i++) {       int from0 = 0, from1 = 0, from2 = 0, total = 0;       for (auto x : inc[i]) {         total++;         if (labels[x] == 0) {           from0++;         } else if (labels[x] == 1) {           from1++;         } else {           from2++;         }       }       if (from2 == total) {         labels[i] = 0;       } else if (from1 == 0) {         labels[i] = 1;       } else {         rem.push_back(i);         labels[i] = 2;       }     }     cout << rem.size() << endl;     for (auto x : rem) cout << x <<    ;     cout << endl;   }   signed main() {     ran();     fast();     int t = 1;     cin >> t;     while (t--) {       solve();     }   }   