#include <bits/stdc++.h>
#define NMAX 1001

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector <int> G[NMAX], GT[NMAX], ctc[NMAX];
vector <bool> viz;
vector <int> postordine;
int nr, K;

void DFS(int nod) {
    viz[nod] = true;
    for(int i = 0; i < G[nod].size(); ++i) {
        if(!viz[G[nod][i]]) {
            DFS(G[nod][i]);
        }
    }
    postordine[++nr] = nod;
}

void DFST(int nod) {
    viz[nod] = false;
    ctc[K].push_back(nod);
    for(int i = 0; i < GT[nod].size(); ++i) {
        if(viz[GT[nod][i]]) {
            DFST(G[nod][i]);
        }
    }
}

int main() {
    int N, M;
    fin>>N>>M;
    viz.resize(NMAX, false);
    postordine.resize(NMAX, 0);
    for(int x, y, i = 0; i < M; ++i) {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i = 1; i <= N; ++i) {
        if(!viz[i]) {
            DFS(i);
        }
    }
    for(int i = N; i > 0; --i) {
        if(viz[postordine[i]]) {
            K += 1;
            DFST(postordine[i]);
        }
    }
    fout<<K<<'\n';
    for(int i = 1; i <= K; i++)
    {
        for(int j = 0; j < ctc[i].size(); j++)
            fout << ctc[i][j] << ' ';
        fout << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}