Даше исправленное

#include <iostream>
#include <vector>

using namespace std;

int n, m;
vector<vector<int>> G(20000);
vector<vector<int>> GR(20000);
vector<int> used(20000);
vector<int> order;
vector<int> comp;

void dfs(int v) {
    used[v] = 1;
    for (int i = 0; i < G[v].size(); i++) {
        int actual_v = G[v][i];
        if (used[actual_v] == 0) {
            dfs(actual_v);
        }
    }
    order.push_back(v);
}

void dfs_R(int v) {
    used[v] = 1;
    comp.push_back(v);
    for (int i = 0; i < GR[v].size(); i++) {
        int actual_v = GR[v][i];
        if (used[actual_v] == 0) {
            dfs_R(actual_v);
        }
    }
}

int main() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int f, t;
        cin >> f >> t;
        G[f - 1].push_back(t - 1);
        GR[t - 1].push_back(f - 1);
    }

    for (int i = 0; i < n; i++) {
        if (used[i] == 0) {
            dfs(i);
        }
    }

    for (int i = 0; i < n; i++) {
        used[i] = 0;
    }

    int k = 1;
    vector<int> comp_number(n);
    vector<int> comp_v;
    for (int i = 0; i < n; i++) {
        int actual_v = order[n - i - 1];
        if (used[actual_v] == 0) {
            dfs_R(actual_v);
            for (int j = 0; j < comp.size(); j++) {
                comp_number[comp[j]] = k;
            }
            comp_v.push_back(comp[0]);
            k = k + 1;
            comp.clear();
        }
    }

    vector<int> FS(k - 1);

    int st = k;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < G[i].size(); j++) {
            int a = i;
            int b = G[i][j];
            if (comp_number[a] != comp_number[b]) {
                if (FS[comp_number[a] - 1] == 0)
                    st = st - 1;
                FS[comp_number[a] - 1] = 1;
            }
        }
    }
    cout << st - 1 << endl;
    for (int i = 0; i < k - 1; i++) {
        if (FS[i] == 0) {
            cout << comp_v[i] + 1 << endl;
        }
    }
    return 0;
}