#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <vector <int>> la; //lista adiacenta
vector <vector <int>> lat; //lista adiacenta inversa
vector <vector <int>> rezultat;
int nrc=0;
vector <int> nivel;
vector <int> stiva; //pentru dfs

void dfs(int s)
{
    for(long unsigned int i=0;i<la[s].size();i++)
    {
        if(nivel[la[s][i]]==0)
        {
            nivel[la[s][i]]=1;
            dfs(la[s][i]);
        }
    }
    //punem nodul in stiva dupa ce ii parcurgem toti vecinii
    stiva.push_back(s);
}
void dfst(int s) //dfs invers
{
    rezultat[nrc].push_back(s); //adaug in componenta actuala
    nivel[s]=2;
    for(long unsigned int i=0;i<lat[s].size();i++)
    {
        if(nivel[lat[s][i]]==1)
        {
            dfst(lat[s][i]);
        }
    }
}
int main()
{
    int x,y,n,m,nod;
    fin>>n>>m;
    //fara resize da eroare
    la.resize(n+1);
    lat.resize(n+1);
    nivel.resize(n+1);
    rezultat.resize(n+1);
    //construim lista de adiecanta si inversa
    for(int i=0;i<m;i++)
    {
        fin>>x>>y;
        la[x].push_back(y);
        lat[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
    {   nivel[i] = 0;}
    //Kosaraju
    //dfs normal
    for(int i=1;i<=n;i++)
    {
        if(nivel[i]==0)
        {
            nivel[i]=1;
            dfs(i);
        }
    }
    //scot cate un elem de pe stiva, daca acesta nu a fost vizitat pornesc
    //un nou dfs pe inversa, insemnand ca am o componenta conexa noua
    while(!stiva.empty())
    {
        nod=stiva.back();
        stiva.pop_back();
        if(nivel[nod]==1)
        {
            nrc++;
            dfst(nod);
        }
    }
    fout<<nrc<<endl;
    for(int i=1;i<=nrc;i++)
    {
        for(long unsigned int j=0;j<rezultat[i].size();j++)
        {
            fout<<rezultat[i][j]<<" ";
        }
        fout<<endl;
    }
    return 0;
}