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

#define NMax 100005

using namespace std;

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

int N, VIZ[NMax], comp_conexe;
vector <int> Graf[NMax], Graf_t[NMax], sol[NMax];
stack <int> Stiva;


void DFS(int nod)
{
    VIZ[nod] = 1;

    for(unsigned int i = 0; i < Graf[nod].size(); ++ i)
        if(VIZ[Graf[nod][i]] == 0)
            DFS(Graf[nod][i]);

    Stiva.push(nod);
}

void DFS_2(int nod_2)
{
    VIZ[nod_2] = 2;
    sol[comp_conexe].push_back(nod_2);

    for(unsigned int i = 0; i < Graf_t[nod_2].size(); ++ i)
        if(VIZ[Graf_t[nod_2][i]] == 1)
            DFS_2(Graf_t[nod_2][i]);
}

void Kosaraju()
{
    for(int i = 1; i <= N; ++ i)
        if(VIZ[i] == 0)
            DFS(i);

    while( !Stiva.empty() )
    {
        int nodCurent = Stiva.top();
        Stiva.pop();

        if(VIZ[nodCurent] == 1)
        {
            comp_conexe ++;
            DFS_2(nodCurent);
        }
    }
}

int main()
{
    int M, x, y;

    fin >> N >> M;
    for(int i = 1; i <= M; ++ i)
    {
        fin >> x >> y;

        Graf[x].push_back(y);
        Graf_t[y].push_back(x);
    }
    fin.close();

    Kosaraju();

    fout << comp_conexe << '\n';
    for(int i = 1; i <= comp_conexe; ++ i, fout << '\n')
        for(unsigned int j = 0; j < sol[i].size(); ++ j)
            fout << sol[i][j] << ' ';
    fout.close();

    return 0;
}