#include <fstream>
#include <vector>
using namespace std;

#define NMax 100001

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

int n,m,nr,nrsol;
int viz[NMax],postordine[NMax];
vector<int> v[NMax],w[NMax],sol[NMax];

void DFS(int s)
{
    int i,e;
    viz[s]=1;
    e=v[s].size();
    for(i=0;i<e;i++) if(viz[v[s].at(i)]==0) DFS(v[s].at(i));
    postordine[++nr]=s;
}

void DFST(int s)
{
    int i,e;
    viz[s]=0;
    sol[nrsol].push_back(s);
    e=w[s].size();
    for(i=0;i<e;i++) if(viz[w[s].at(i)]==1) DFST(w[s].at(i));
}

int main()
{
    int i,a,b;

    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>a>>b;
        v[a].push_back(b);
        w[b].push_back(a);
    }

    for(i=1;i<=n;i++) if(viz[i]==0) DFS(i);
    for(i=n;i>=1;i--) if(viz[postordine[i]]==1) {nrsol++;DFST(postordine[i]);}

    g<<nrsol<<"\n";
    for(i=1;i<=nrsol;i++)
    {
        b=sol[i].size();
        for(a=0;a<b;a++) g<<sol[i].at(a)<<" ";
        g<<"\n";
    }

    f.close();
    g.close();
    return 0;
}