#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

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

const int NMAX = 100000;

int M, N, nrc;

vector<int> G[NMAX+1], GT[NMAX+1], CTC[NMAX+1], Post;
bool viz[NMAX+1];

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

void DFS(int nod) {
    viz[nod] = 1;
    for (const auto &x : G[nod])
        if(!viz[x])
            DFS(x);
    Post.push_back(nod);
}

void DFSGT(int nod) {
    viz[nod] = 0;
    CTC[nrc].push_back(nod);
    for(const auto &x : GT[nod])
        if(viz[x])
            DFSGT(x);
}

void componente() {
    for(int i=1; i<=N; i++)
        if(!viz[i])
            DFS(i);
    for (int i = Post.size()-1; i>=0; i--)
        if(viz[Post[i]]) {
            nrc++;
            DFSGT(Post[i]);
        }
}

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

int main()
{
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}