#include <bits/stdc++.h>

using namespace std;

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

int n, m, x, y, cnx;

vector <int> G[100005], GT[100005], v, N[100005];

bitset <100005> viz1, viz;

void DFS (int nod)
{
    int curent;

    viz[nod] = 1;

    for (int i=0; i<G[nod].size(); i++)
    {
        curent = G[nod][i];
        if (!viz[curent]) DFS(curent);
    }
    v.push_back(nod);
}

void DFS1 (int nod)
{
    int curent;

    viz1[nod] = 1;
    N[cnx].push_back(nod);

    for (int i=0; i<GT[nod].size(); i++)
    {
        curent = GT[nod][i];
        if (!viz1[curent]) DFS1(curent);
    }
}

int main()
{
    fin >> n >> m;
    while(m--)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for (int i=1; i<=n; i++)
        if (viz[i] == 0) DFS(i);
    for (int i=v.size()-1; i>=0; i--)
        if (!viz1[v[i]])
        {
            cnx++;
            DFS1(v[i]);
            sort(N[cnx].begin(), N[cnx].end());
        }
    fout << cnx << "\n";
    int curent;
    for (int i=1; i<=cnx; i++)
    {
        for (int j=0; j<N[i].size(); j++)
            fout << N[i][j] << " ";
        fout << "\n";
    }
    return 0;
}