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

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

const int MAX = 100005;
using VI = vector<int>;
vector<VI> G, Gt;
vector<VI> rez;
VI x;
int N, M;
bool used[MAX];
int m1[MAX], m2[MAX];
int nrez;

void Read();
void DF1( int i, int nod );
void DF2( int i, int nod );
void Solve();
void Write();

int main()
{
    Read();
    Solve();
    Write();

    fin.close();
    fout.close();
    return 0;
}

void Read()
{
    int j, x, y;

    fin >> N >> M;

    G.resize(N + 1);
    Gt.resize(N + 1);
    rez.resize(N + 1);

    for ( j = 1; j <= M; j++ )
    {
        fin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
}

void DF1( int i, int nod )
{
    x.push_back(nod);
    used[nod] = 1;
    for ( const auto& x : G[nod] )
        if ( !used[x] )
        {
            DF1(i, x);
        }
}

void DF2( int i, int nod )
{
    m2[nod] = i;
    for ( const auto& x : Gt[nod] )
        if ( !m2[x] )
        {
            DF2(i, x);
        }
}

void Solve()
{
    int i;
    nrez = 1;

    x.push_back(0);

    for ( i = 1; i <= N; i++ )
        if ( !used[i] )
            DF1(i, i);

    for ( auto it = x.begin() + 1; it != x.end(); ++it )
    {
       // cout << *it; cin.get();
        if ( !m2[*it] )
        {
            DF2(nrez, *it);
            nrez++;
        }
    }

    for ( i = 1; i <= N; i++ )
        rez[m2[i]].push_back(i);
}

void Write()
{
    int i;

    fout << nrez - 1 << '\n';
    for ( i = 1; i < nrez; i++ )
    {
        for ( const auto& x : rez[i] )
            fout << x << ' ';
        fout << '\n';
    }
}