#include <iostream>
#include <fstream>
#include <vector>
#include <deque>
#define NMAX 100002
using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
vector<int>gi[NMAX], gf[NMAX], comp[NMAX];
deque <int> t;
bool viz1[NMAX], viz2[NMAX];
int n, m, nr_componente=0;

void DFS1(int x)
{
    viz1[x]=1;
    for(int i=0; i<gi[x].size(); i++){
        if(!viz1[gi[x][i]])
            DFS1(gi[x][i]);
    }
    t.push_back(x); //adaug in lista elementelor sortate topologic
}
void DFS2(int x)
{
    comp[nr_componente].push_back(x);
    viz2[x]=1;
    for(int i=0; i<gf[x].size(); i++){
        if(!viz2[gf[x][i]])
            DFS2(gf[x][i]);
    }
}
void sortareTopologica()
{
    for(int i=1; i<=n; i++){
        if(!viz1[i]) DFS1(i);
    }
}
int main()
{
    fin>>n>>m;
    int i, j, x, y;
    for(i=1; i<=m; i++){
        fin>>x>>y;
        gi[x].push_back(y);
        gf[y].push_back(x);
    }
    sortareTopologica();

    for(i=t.size()-1; i>=0; i--){
        if(!viz2[t[i]]){
            //am gasit o noua componenta
            nr_componente++;
            DFS2(t[i]);
        }
    }

    fout<<nr_componente<<"\n";
    for(i=1; i<=nr_componente; i++){
        for(j=0; j<comp[i].size(); j++) fout<<comp[i][j]<<' ';
        fout<<"\n";
    }
}