#include <fstream>
#include <vector>
#define NMAX 100001

using namespace std;

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

int n, m, parcurgere;
bool viz[NMAX], vizT[NMAX];

vector <int> G[NMAX], GT[NMAX], solutie[NMAX];
vector <int> postordine;


void citire();
void DFS1(int poz);
void DFS2(int poz);

int main()
{
    int i, j;
    citire();
    for(i=1;i<=n;++i)
    {
        if(!viz[i]) DFS1(i);
    }
    for(i=n-1;i>=0;--i)
    {
        if(!vizT[postordine[i]])
        {
            ++parcurgere;
            DFS2(postordine[i]);
        }
    }
    fout<<parcurgere<<endl;
    for(i=1;i<=parcurgere;++i)
    {
        for(j=0;j<solutie[i].size();++j)
            fout<<solutie[i][j]<<' ';
        fout<<endl;
    }
    fout.close();
    return 0;
}

void citire()
{
    fin>>n>>m;
    int x, y, i;
    for(i=0; i<m; ++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS1(int k)
{
    viz[k]=true;
    unsigned int i;
    for(i=0; i<G[k].size();++i)
    {
        if(!viz[G[k][i]])
        {
            DFS1(G[k][i]);
        }
    }
    postordine.push_back(k);
}

void DFS2(int k)
{
    unsigned int i;
    vizT[k]=true;
    solutie[parcurgere].push_back(k);
    for(i=0; i<GT[k].size(); ++i)
    {
        if(!vizT[GT[k][i]])
        {
            DFS2(GT[k][i]);
        }
    }
}