#include <fstream>
#include <vector>
using namespace std;

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

vector<vector<int> > vec, vect, comp;
vector<bool> viz;
vector<int> ord;

void dfs1(int nod)
{
    viz[nod] = true;
    for (int i = 0; i < (int)vec[nod].size(); i++)
    {
        int urm = vec[nod][i];
        if (!viz[urm])
            dfs1(urm);
    }
    ord.push_back(nod);
}

void dfs2(int nod, int c)
{
    viz[nod] = true;
    comp[c].push_back(nod);
    for (int i = 0; i < (int)vect[nod].size(); i++)
    {
        int urm = vect[nod][i];
        if (!viz[urm])
            dfs2(urm, c);
    }
}

int main()
{
    int n, m;
    fin >> n >> m;

    vec.resize(n + 1);
    vect.resize(n + 1);
    for (int i = 0; i < m; i++)
    {
        int a, b;
        fin >> a >> b;
        vec[a].push_back(b);
        vect[b].push_back(a);
    }

    viz.assign(n + 1, false);
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs1(i);

    viz.assign(n + 1, false);
    for (int i = n - 1; i >= 0; i--)
    {
        int nod = ord[i];
        if (!viz[nod])
        {
            comp.push_back(vector<int>());
            dfs2(nod, comp.size() - 1);
        }
    }

    fout << comp.size() << "\n";
    for (int i = 0; i < (int)comp.size(); i++)
    {
        for (int j = 0; j < (int)comp[i].size(); j++)
            fout << comp[i][j] << " ";
        fout << "\n";
    }
    return 0;
}