///componente tare conexe
#include<fstream>
#include<vector>
#include<stack>
#include<cstring>
#define In "ctc.in"
#define Out "ctc.out"
#define Nmax 100001
using namespace std;
int n,nr;
bool viz[Nmax];
stack< int >St;
vector< int >graf[Nmax];
vector< int >graf_t[Nmax];
vector< int > sol[Nmax];
//graf_t = graf transpus
inline void Citire()
{
    int m,x,y;
    ifstream f(In);
    f>>n>>m;
    while(m--)
    {
        f>>x>>y;
        graf[x].push_back(y);
        graf_t[y].push_back(x);
    }
    f.close();
}

inline void Dfs(int nod)
{
    viz[nod] = true;
    St.push(nod);
    for(vector<int>::iterator it = graf[nod].begin();it!=graf[nod].end();it++)
        if(viz[*it]==false)
            Dfs(*it);

}
inline void Parcurgere_adancime()
{
    for(int i=1;i<=n;i++)
        if(viz[i]==false)
            Dfs(i);
}

inline void Dfs_t(int nod)
{
    viz[nod] = true;
    sol[nr].push_back(nod);
    for(vector<int>::iterator it = graf_t[nod].begin();it!=graf_t[nod].end();it++)
        if(viz[*it]==false)
            Dfs_t(*it);
}

inline void Parcurgere_adancime_t()
{
    memset(viz,0,sizeof(viz));
    while(!St.empty())
    {
        if(viz[St.top()]==false)
        {
            nr++;
            Dfs_t(St.top());
        }
        St.pop();
    }
}

inline void Afisare()
{
    ofstream g(Out);
    g<<nr<<"\n";
    vector < int >::iterator it;
    for(int i=1;i<=nr;i++)
    {
        for(it=sol[i].begin();it!=sol[i].end();it++)
            g<<*it<<" ";
        g<<"\n";
    }
    g.close();
}
int main()
{
    Citire();
    Parcurgere_adancime();
    Parcurgere_adancime_t();
    Afisare();
    return 0;
}