// https://goo.gl/fBmFxu
#include <bits/stdc++.h>
using namespace std;

#define NMAX        100009
#define MMAX        200009
#define kInf        (1 << 30)
#define kInfLL      (1LL << 60)
#define kMod        666013
#define edge pair<int, int>
#define x first
#define y second

// number of tests from "in"
int test_cnt = 1;
void clean_test();

// your global variables are here
int n, m;
vector<int> G[NMAX], T[NMAX];
bitset<NMAX> visited;
vector<int> topsort;
vector<vector<int> > all_ctc;

void dfs(int node) {
    visited[node] = 1;

    for (auto &x : G[node]) {
        if (!visited[x]) {
            dfs(x);
        }
    }

    topsort.push_back(node);
}


void dfs_trans(int node, vector<int> &current_ctc) {
    visited[node] = 0;
    current_ctc.push_back(node);

    for (auto &x : T[node]) {
        if (visited[x]) {
            dfs_trans(x, current_ctc);
        }
    }
}

// your solution is here
void solve() {
    cin >> n >> m;

    for (int i = 1; i <= m; ++i) {
        int x, y;
        cin >> x >> y;

        G[x].push_back(y);
        T[y].push_back(x);
    }

    for (int i = 1; i <= n; ++i) {
        if (!visited[i]) {
            dfs(i);
        }
    }

    reverse(topsort.begin(), topsort.end());
    for (auto &x : topsort) {
        if (visited[x]) {
            vector<int> current_ctc;
            dfs_trans(x, current_ctc);

            all_ctc.push_back(current_ctc);
        }
    }

    cout << all_ctc.size() << "\n";
    for (auto &ctc : all_ctc) {
        for (auto &x : ctc) {
            cout << x << " ";
        }
        cout << "\n";
    }

    if (test_cnt > 0) {
        clean_test();
    }
}


void clean_test() {
    // clean if needed
    visited.reset(); // reset all
    topsort.clear();
    all_ctc.clear();

    for (int i = 1; i <= n; ++i) {
        if (G[i].size())  {
            G[i].clear();
        }
    }

    // clean every shit
    n = m  = 0;
}

int main() {
    // din cauza ca fac redirectari, salvez starea lui cin si cout
    auto cin_buff = cin.rdbuf();
    auto cout_buff = cout.rdbuf();

    // las liniile urmatoare daca citesc din fisier
    ifstream fin("ctc.in");
    cin.rdbuf(fin.rdbuf()); // save and redirect

    // las liniile urmatoare daca afisez in fisier
    ofstream fout("ctc.out");
    cout.rdbuf(fout.rdbuf()); // save and redirect


//     cin >> test_cnt;
    while (test_cnt--) {
        solve();
    }

    // restore pentru cin si cout
    cin.rdbuf(cin_buff);
    cout.rdbuf(cout_buff);

    return 0;
}