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

#define Nmax 100005

using namespace std;

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

int vf, muchii;

int Vizitat[Nmax];
vector < int > Numbers[Nmax];
vector < int > Numbers_SensInversMuchii[Nmax];
vector < int > SalvamCTC[Nmax];

stack < int > Stiva;

int compconex, ctc;

inline void DFS( int Nod )
{
    int Vecin;

    Vizitat[Nod] = 1;
    for( unsigned int i = 0; i < Numbers[Nod].size(); ++ i )
    {
        Vecin = Numbers[Nod][i];
        if( !Vizitat[Vecin] )
            DFS(Vecin);
    }//cand am parcurs toti vecinii nodului
    Stiva.push(Nod);

}

inline void DFS_2( int Nod )
{
    int Vecin;

    SalvamCTC[ctc].push_back(Nod);
    Vizitat[Nod] = 2;

    for( unsigned int i = 0; i < Numbers_SensInversMuchii[Nod].size(); ++ i )
    {
        Vecin = Numbers_SensInversMuchii[Nod][i];
        if( Vizitat[Vecin] == 1 )
            DFS_2(Vecin);
    }

}

int main()
{
    fin >> vf >> muchii;
    for( int i = 1; i <= muchii; ++ i )
    {
        int x, y;
        fin >> x >> y;
        Numbers[x].push_back(y);
        Numbers_SensInversMuchii[y].push_back(x);
    }

    for( int i = 1; i <= vf; ++ i )
        if( !Vizitat[i] )
            DFS(i);

    while( !Stiva.empty() )
    {
        int Numar = Stiva.top();
        if( Vizitat[Numar] == 1 )
        {
            ctc++;
            DFS_2(Numar); // parcurgem transpusa grafului
        }
        Stiva.pop();
    }
    fout << ctc << "\n";
    for( int i = 1; i <= ctc; ++ i )
    {
        for( unsigned int j = 0; j < SalvamCTC[i].size(); ++ j )
        {
            fout << SalvamCTC[i][j] << " ";
        }
        fout << "\n";
    }
    return 0;
}