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

using namespace std;

#define NMAX 100005

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

int n, m, comp_cur;
bool viz[NMAX];
vector<int> G[NMAX], GT[NMAX], CTC[NMAX];
stack<int> st;

void citire() {
    f >> n >> m;
    int x, y;
    for (int i = 1; i <= m; ++i) {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

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

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

void dfs_graf_transpus(int x) {
    CTC[comp_cur].push_back(x);
    viz[x]=true;
    for (auto &nod: GT[x])
        if (!viz[nod])
            dfs_graf_transpus(nod);
}

void Kosaraju() {
    //Parcurgere graf
    for (int i = 1; i <= n; ++i)
        if (!viz[i])
            dfs_graf(i);

    resetare_viz();

    //Parcurgere graf transpus
    while (!st.empty()) {
        int nod = st.top();
        st.pop();
        if (viz[nod])
            continue;
        comp_cur++;
        dfs_graf_transpus(nod);
    }
}

void afisare() {
    g << comp_cur << '\n';
    for (int i = 1; i <= comp_cur; ++i) {
        for (auto &nod: CTC[i])
            g << nod << ' ';
        g << '\n';
    }
}

int main() {
    citire();
    Kosaraju();
    afisare();
}