/* 
 * File:   main.cpp
 * Author: virtualdemon
 *
 * Created on May 13, 2010, 3:40 PM
 */
#include <stack>
#include <vector>
#include <cstdlib>
#include <fstream>
#include <iterator>
#define Nmax 100011

/*
 *
 */
using namespace std;
int nrct, indx;
bool InS[Nmax];
int idx[Nmax], lowlink[Nmax];
stack< int > S;
vector< int > G[Nmax], ctc[Nmax];
inline void GetTc( int x )
{
    int v;
    ++nrct;
    do
    {
        v=S.top(); S.pop();
        InS[v]=false;
        ctc[nrct].push_back(v);
    }while( v != x );
}
inline void DFS( int  x )
{
    vector< int >::const_iterator it=G[x].begin(), iend=G[x].end();
    S.push(x);
    InS[x]=true;
    idx[x]=lowlink[x]=++indx;
    for( ; it < iend; ++it )
        if( !idx[*it] )
        {
            DFS(*it);
            lowlink[x]=min( lowlink[x], lowlink[*it] );
        }
        else if( InS[*it] )
                lowlink[x]=min( lowlink[x], lowlink[*it] );
    if( idx[x] == lowlink[x] )
        GetTc(x);
}
int main( void )
{
    int N, M, x, y;
    ifstream in( "ctc.in" );
    for( in>>N>>M; M; --M )
    {
        in>>x>>y;
        G[x].push_back(y);
    }
    for( x=1; x <= N; ++x )
        if( !idx[x] )
            DFS(x);
    ofstream out( "ctc.out" );
    out<<nrct<<'\n';
    for( x=1; x <= nrct; ++x )
    {
        copy( ctc[x].begin(), ctc[x].end(), ostream_iterator<int>( out, " " ) );
        out<<'\n';
    }
    return EXIT_SUCCESS;
}