#include <fstream>
#include <vector>

using namespace std;
const int NMAX=100001;

int N, M, nrc;

vector <int> G[NMAX], GT[NMAX],
       CTC[NMAX],
       Post;

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);
}

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()
{
    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(int x:CTC[i])
            g<<x<<' ';
        g<<'\n';
    }
}

int main()
{
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}