#include <vector>
#include <fstream>
#include <iostream>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int NMax = 100000;
vector <int> G[NMax + 5],GT[NMax + 5];
vector<int> CTC[NMax + 5];
int N,M,NrCTC; int Use[NMax + 5];
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 DFSP(int Nod)
{
    Use[Nod] = 1;
    for(auto Vecin : G[Nod])
    if(!Use[Vecin])
        DFSP(Vecin);
}
void DFSM(int Nod)
{
    Use[Nod] = 2; CTC[NrCTC].push_back(Nod);
    for(auto Vecin : GT[Nod])
    if(Use[Vecin] == 1)
        DFSM(Vecin);
}

void Print()
{
    fout << NrCTC << "\n";
    for(int i = 1; i <= NrCTC; ++i)
    {
        for(auto Nod : CTC[i])
            fout << Nod << " ";
        fout << "\n";
    }
}

int main()
{
    Read();

    for(int i = 1 ; i <= N; ++i)
    {
        if(Use[i] == 0)
        {
            NrCTC++;
            DFSP(i);
            DFSM(i);
            for(int i = 1; i <= N; ++i)
                if(Use[i] == 1)
                    Use[i] = 0;
        }
    }

    Print();

    return 0;
}