/// Alg. Kosaraju de complexitate O(n+m) ia 100 pct. pe infparena.ro
#include <bits/stdc++.h>
#define NM 100005
using namespace std;
ifstream f("ctc.in"); ofstream g("ctc.out");
int n,m,timp,nr,F[NM],Use[NM];
vector<int> G[NM],GT[NM],ctc[NM];
void DFS(int x)
{   Use[x]=1;
    for(unsigned int j,i=0;i<G[x].size();i++)
    {   j=G[x][i];
        if(!Use[j]) DFS(j);
    }
    F[++timp]=x;
}
void DFST(int x)
{   Use[x] = 1;
    ctc[nr].push_back(x);
    for(unsigned int j,i = 0;i<GT[x].size(); i++)
    {   j=GT[x][i];
        if(!Use[j]) DFST(j);
    }
}
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(!Use[i]) DFS(i);
    for(int i=1;i<=n;i++) Use[i]=0; ///resetam vectorul viz
    for(int i=n;i;i--) ///parcurgem in in sens invers vectorul postord
        if(!Use[F[i]]) {nr++; DFST(F[i]);}
    g<<nr<<'\n';
    for(int i=1;i<=nr;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;
}