#include <bits/stdc++.h>
#define N 100005
using namespace std;

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

int n,m;
vector <int> G[N]; ///liste adiacenta graf G
vector <int> GT[N];///liste adiacenta graf transpus
vector <int> CTC[N]; /// memorare componente tare conexe

stack <int> S; ///nodurile in ordinea timpilor de final

bool viz[N]; ///DFS pe graful G
bool vizit[N];///DFS pe graful GT
int nc;/// numarul de componente tare conexe

void Citire()
{
    int i,x,y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS(int x)
{
    viz[x]=1;
    for(int i=0;i<G[x].size();i++)
        if(!viz[G[x][i]]) DFS(G[x][i]);
    S.push(x);
}

void TimpiFinali()
{
    int i;
    for(i=1;i<=n;i++)
        if(!viz[i]) DFS(i);
}

void DFST(int x)
{
    vizt[x]=1;
    CTC[nc].push_back(x);
    for(int i=0;i<GT[x].size();i++)
        if(!vizt[GT[x][i]])
            DFST(GT[x][i]);
}

void ComponenteTareConexe()
{
    int x;
    while(!S.empty())
    {
        x=S.top();S.pop();
        if(vizt(x))
        {
            nc++;
            DFST(x);
        }
    }
}

void Afisare()
{
    int i,j;
    fout<<nc<<"/n";
    for(i=1;i<=nc;i++)
    {
        for(j=0;j<CTC[i].size();j++)
            fout<<CTC[i][j]<<" ";
        fout<<"/n";
    }
}

int main()
{
    Citire();
    TimpiFinali();
    ComponenteTareConexe();
    Afisare();
    return 0;
}