#include <bits/stdc++.h>
#define NMax 100006

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, m;
bool viz[NMax];
int sir[NMax], K, nrcc;
vector <int> L[NMax], G[NMax];

inline void Citire()
{
    int i, x, y;

    fin >> n >> m;

    for(i = 1; i <= m; i++)
    {
        fin >> x >> y;
        L[x].push_back(y);
        G[y].push_back(x);
    }
}

void DFS1(int nod)
{
    int j, i;

    viz[nod] = 1;
    for(j = 0; j < L[nod].size(); j++)
    {
        i = L[nod][j];
        if(!viz[i])
            DFS1(i);
    }
    sir[++K] = nod;
}

void DFS2(int nod)
{
    int j, i;

    viz[nod] = 1;
    for(j = 0; j < G[nod].size(); j++)
    {
        i = G[nod][j];
        if(!viz[i])
            DFS2(i);
    }
    L[nrcc].push_back(nod);
}

inline void Initializare()
{
    for(int i = 1; i <= n; i++)
        viz[i] = 0;
}
inline void Rezolva()
{
    int i;

    for(i = 1; i <= n; i++)
        if(!viz[i])
            DFS1(i);

    Initializare();

    for(i = K; i >= 1; i--)
    {
        if(!viz[sir[i]])
        {
            nrcc++;
            L[nrcc].clear();
            DFS2(sir[i]);
        }
    }

    fout << nrcc << "\n";
    for(i = 1; i <= nrcc; i++)
    {
        for(int j = 0; j < L[i].size(); j++)
            fout << L[i][j] << " ";
        fout << "\n";
    }
}
int main()
{
    Citire();
    Rezolva();
    return 0;
}