#include <fstream>
#include <vector>
#define Nmax 100005

using namespace std;

int N,st[Nmax],top,nrsol;
vector <int> L[Nmax],T[Nmax],sol[Nmax];
bool viz[Nmax];

inline void Read()
{
    int i,x,y,M;
    ifstream fin("ctc.in");
    fin>>N>>M;
    for(i=1;i<=M;++i)
    {
        fin>>x>>y;
        L[x].push_back(y);
        T[y].push_back(x);
    }
    fin.close();
}

inline void Dfs(int nod)
{
    int i,len,j;
    len=L[nod].size();
    viz[nod]=true;
    for(i=0;i<len;++i)
    {
        j=L[nod][i];
        if(!viz[j])
            Dfs(j);
    }
    st[++top]=nod;
}

inline void Dfs2(int nod)
{
    int i,len,j;
    len=T[nod].size();
    viz[nod]=true;
    for(i=0;i<len;++i)
    {
        j=T[nod][i];
        if(!viz[j])
            Dfs2(j);
    }
    sol[nrsol].push_back(nod);
}

inline void Solve()
{
    int i,j,len,nod;
    for(i=1;i<=N;++i)
        if(!viz[i])
            Dfs(i);
    for(i=1;i<=N;++i)
        viz[i]=false;
    while(top>0)
    {
        nod=st[top--];
        if(!viz[nod])
        {
            ++nrsol;
            Dfs2(nod);
        }
    }
    ofstream fout("ctc.out");
    fout<<nrsol<<"\n";
    for(i=1;i<=nrsol;++i)
    {
        len=sol[i].size();
        for(j=0;j<len;j++)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
    fout.close();
}

int main()
{
    Read();
    Solve();
    return 0;
}