#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

int n, m;
vector<vector<int> > gr(100100);
vector<vector<int> > inv(100100);
vector<bool> used(100100);
vector<vector<int> > ans;

vector<int> verif;
vector<int> comp;

void dfs(int root) {

    used[root] = true;
    for (auto &x : gr[root]) {
        if (!used[x]) {
            dfs(x);
        }
    }
    verif.push_back(root);

}

void DFS(int root) {

    used[root] = true;
    comp.push_back(root);
    for (auto &x : inv[root]) {
        if (!used[x]) {
            DFS(x);
        }
    }

}

int main() {

    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> m;

    for (int i = 1; i <= m; i++) {
        int a, b;
        cin >> a >> b;
        gr[a].push_back(b);
        inv[b].push_back(a);
    }

    for (int i = 1; i <= n; i++) {
        if (used[i]) {
            continue;
        }

        dfs(i);
    }

    for (int i = 1; i <= n; i++) {
        used[i] = false;
    }

    reverse (verif.begin() , verif.end());

    for (auto &x : verif){
        if (!used[x]){
            comp.clear();
            DFS(x);
            ans.push_back(comp);
        }
    }

    cout << ans.size() << '\n';

    for (auto &x : ans) {
        for (auto &y : x) {
            cout << y << " ";
        }
        cout << '\n';
    }


    return 0;
}