#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int NMax = 100000;
vector <int> G[NMax+5],GT[NMax+5],CTC[NMax+5];
int Use[NMax+5],Sort[NMax+5];
int N,M,NrCtc;
void Read()
{
    fin >> N >> M;
    for(int i = 1 ; i <= M; ++i)
    {
        int x,y;
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void DFST(int Nod)
{
    Use[Nod] = 1;
    for(int i = 0; i < (int)G[Nod].size(); ++i)
    {
        int Vecin = G[Nod][i];
        if(Use[Vecin] == 0)
            DFST(Vecin);
    }
    Sort[++Sort[0]]=Nod;
}
void DFS(int Nod)
{
    Use[Nod] = 0; CTC[NrCtc].push_back(Nod);
    for(int i = 0; i < (int)GT[Nod].size(); ++i)
    {
        int Vecin = GT[Nod][i];
        if(Use[Vecin] == 1)
            DFS(Vecin);
    }
}

void Print()
{
    fout << NrCtc << "\n";
    for(int i = 1; i <= NrCtc; ++i)
    {
        for(int j = 0; j < (int)CTC[i].size(); ++j)
            fout << CTC[i][j]<< " ";
        fout << "\n";
    }
}

int main()
{
    Read();
    for(int i = 1; i <= N; ++i)
        if(!Use[i])
            DFST(i);

    for(int i = N; i > 0; --i)
        {
            if(Use[Sort[i]] == 1)
            {
                NrCtc++;
                DFS(Sort[i]);
            }
        }

    Print();
    return 0;
}