#include <fstream>
#include <vector>
using namespace std;
const int NMAX=100001;

int N,M,nrc;

vector <int> G[NMAX], GT[NMAX],
       CTC[NMAX], ///ctc[i]=lista nodurilor din a i a c.t.c;
       Post; ///lista nodurilor lui G in ordinea finalizarii acestora in parcurgerea DFS
bool viz[NMAX];

ifstream f("ctc.in");
ofstream g("ctc.out");

void citire()
{
    int x,y;
    f>>N>>M;
    while (M--)
    {
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int vf)
{
    viz[vf]=1;
    for (int x:G[vf])
        if (viz[x]==0)
            dfs(x);
    Post.push_back(vf); ///s a finalizat parcurgerea din vf
}

void dfsGT(int vf)
{
     viz[vf]=0;
     CTC[nrc].push_back(vf);
     for (int x:GT[vf])
        if (viz[x]==1)
            dfsGT(x);
}

void componente() ///algoritmul Kosaraju-Sharir (1978)
{
    int i;
    for (i=1;i<=N;i++)
        if (viz[i]==0)
            dfs(i);
    for (i=Post.size()-1;i>=0;--i)
        if (viz[Post[i]]==1)
        {
            nrc++;
            dfsGT(Post[i]);
        }

}

void afisare()
{
    g<<nrc<<'\n';
    for (int i=1;i<=nrc;i++)
    {
        for (const auto &x:CTC[i])
            g<<x<<' ';
        g<<'\n';
    }
}
int main()
{
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}