#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
//ifstream in("date.in");
ifstream in("ctc.in");
//ofstream out("date.out");
ofstream out("ctc.out");

const int NMax = 1e5;
int N, M, NrConexe;
vector <int> G1[NMax], G2[NMax], CompConx[NMax];
int UseP[NMax], UseN[NMax];

void Read(){
    in >> N >> M;
    int x, y;
    while (M--){
        in >> x >> y;
        G1[x].push_back(y);
        G2[y].push_back(x);
    }
}

void DFS1(int Nod){
    UseN[Nod] = NrConexe;
    for (int i = 0; i < (int)G1[Nod].size(); ++i){
        int Vecin = G1[Nod][i];
        if (!UseN[Vecin])
            DFS1(Vecin);
    }
}

void DFS2(int Nod){
    UseP[Nod] = NrConexe;
    for (int i = 0; i <(int)G2[Nod].size(); ++i){
        int Vecin = G2[Nod][i];
        if (!UseP[Vecin])
            DFS2(Vecin);
    }
}

void Solve(){
    for (int i = 1; i <= N; ++i)
        if (!UseN[i]){
            NrConexe ++;
            DFS1(i);
            DFS2(i);
            for (int j = 1; j <= N; ++j)
                if (UseN[j] != UseP[j])
                    UseN[j] = UseP[j] = 0;
        }
    for (int i = 1; i <= N; ++i)
        CompConx[UseN[i]].push_back(i);
}

void Print(){
    out << NrConexe << '\n';
    for (int i = 1; i <= NrConexe; out << '\n', ++i)
        for (int j = 0; j < (int)CompConx[i].size(); ++j)
            out << CompConx[i][j] << " ";
}

int main()
{
    Read();
    Solve();
    Print();
    return 0;
}