#include <bits/stdc++.h>
#define NM 100005
using namespace std;
ifstream f("ctc.in"); ofstream g("ctc.out");
int n,m,t,k,postord[NM],viz[NM];
vector<int> G[NM],GT[NM],ctc[NM];
void DFS(int x)
{   viz[x]=1;
    for(unsigned int i = 0;i< G[x].size();i++)
    {   int w=G[x][i];
        if(!viz[w]) DFS(w);
    }
    t++;
    postord[t]=x;
}
void DFST(int x)
{   viz[x] = 1;
    ctc[k].push_back(x);
    for(unsigned int i = 0;i<GT[x].size(); i++)
    {   int w=GT[x][i];
        if(!viz[w]) DFST(w);
    }
}
int main()
{   f>>n>>m;
    for(int x,y,i=1;i<=m;i++)
    {   f>>x>>y;
        G[x].push_back(y);///liste de adiacenta ale grafului dat G
        GT[y].push_back(x);///liste de adiacenta ale grafului dat GT
    }
    ///pasul 1
    for(int i=1;i<=n;i++)
        if(!viz[i]) DFS(i);
    for(int i=1;i<=n;i++) viz[i]=0; ///resetam vectorul viz
    for(int i=n;i;i--) ///parcurgem in in sens invers vectorul postord
        if(!viz[postord[i]]) {k++; DFST(postord[i]);}
    g<<k<<'\n';
    for(int i=1;i<=k;i++)
    {   sort(ctc[i].begin(),ctc[i].end());
        for (unsigned int j=0; j < ctc[i].size(); j++) g<<ctc[i][j]<<' ';
        g<<'\n';
    }
    g.close(); f.close(); return 0;
}