#include <bits/stdc++.h>

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector<vector<int>> graf(100001,vector<int>());
vector<vector<int>> transpus(100001,vector<int>());
vector<vector<int>> componente(100001,vector<int>());
vector<int> postordine;
bool viz[100001];
int n,m,nr;
void Citire()
{
    int x,y;
    f>>n>>m;
    for(int i=1;i<=m;++i)
    {
        f>>x>>y;
        graf[x].push_back(y);
        transpus[y].push_back(x);
    }
}

void DFS(int nod)
{
    viz[nod] = true;
    for(vector<int>::iterator it=graf[nod].begin();it!=graf[nod].end();++it)
        if(!viz[*it]) DFS(*it);
    postordine.push_back(nod);
}

void DFST(int nod)
{
    viz[nod] = false;
    componente[nr].push_back(nod);
    for(vector<int>::iterator it=transpus[nod].begin();it!=transpus[nod].end();++it)
        if(viz[*it]) DFST(*it);
}

void Afisare()
{
    g<<nr<<'\n';
    for(int i=1;i<=nr;++i)
    {
        for(vector<int>::iterator it=componente[i].begin();it!=componente[i].end();++it)
            g<<*it<<" ";
        g<<'\n';
    }
}

int main()
{
    Citire();
    for(int i=1;i<=n;++i)
        if(!viz[i]) DFS(i);
    for(vector<int>::reverse_iterator it=postordine.rbegin();it!=postordine.rend();++it)
        if(viz[*it])
        {
            ++nr;
            DFST(*it);
        }
    Afisare();
    return 0;
}