#include <fstream>
#include <vector>
#include <bitset>
#include <stack>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

#define NMAX 100005

int n, m, nrctc;
vector<int> G[NMAX], GT[NMAX];
vector<int> comp[NMAX];
bitset<NMAX> viz;
stack<int> st;

void citire() {
    f >> n >> m;
    int x, y;
    for (int i = 0; i < m; ++i) {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int x) {
    viz.set(x);
    for (auto &nod: G[x])
        if (!viz[nod])
            dfs(nod);
    st.push(x);
}

void dfs_transpus(int x) {
    viz.set(x);
    comp[nrctc].push_back(x);
    for (auto &nod: GT[x])
        if (!viz[nod])
            dfs_transpus(nod);
}

void componente_tare_conexe() {
    //parcurgere graf
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs(i);

    viz.reset();

    //parcurgere graf transpus
    while (!st.empty()) {
        int x = st.top();
        st.pop();
        if (viz[x])
            continue;
        dfs_transpus(x);
        nrctc++;
    }
}

void afisare() {
    g << nrctc << '\n';
    for (int i = 0; i < nrctc; ++i) {
        for (auto &nod: comp[i])
            g << nod << ' ';
        g << '\n';
    }
}

int main() {
    citire();
    componente_tare_conexe();
    afisare();
    return 0;
}