#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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

int n, m, timer;

vector<vector<int>> graph(100001);
vector<bool> pe_stiva(100001, false);
vector<int> timp(100001, 0);
vector<int> low(100001, 0);
vector<int> stiva;
vector<vector<int>> componente;

void dfs(int nod)
{
    timp[nod] = low[nod] = ++timer;
    stiva.push_back(nod);
    pe_stiva[nod] = true;

    for (const auto& vecin : graph[nod])
    {
        if (timp[vecin] == 0)
        {
            dfs(vecin);
            low[nod] = min(low[nod], low[vecin]);
        }
        else if (pe_stiva[vecin])
        {
            low[nod] = min(low[nod], timp[vecin]);
        }
    }

    if (low[nod] == timp[nod])
    {
        vector<int> componenta;
        int varf;

        do
        {
            varf = stiva.back();
            stiva.pop_back();
            pe_stiva[varf] = false;
            componenta.push_back(varf);
        } while (varf != nod);

        componente.push_back(componenta);
    }
}

int main()
{

    fin >> n >> m;

    for (int i = 1; i <= m; ++i)
    {
        int nod1, nod2;
        fin >> nod1 >> nod2;
        graph[nod1].push_back(nod2);
    }

    for (int i = 1; i <= n; ++i)
    {
        if (timp[i] == 0)
        {
            dfs(i);
        }
    }

    fout << componente.size() << "\n";
    for (size_t i = 0; i < componente.size(); ++i)
    {
        for (size_t j = 0; j < componente[i].size(); ++j)
        {
            if (j > 0)
            {
                fout << " ";
            }
            fout << componente[i][j];
        }
        fout << "\n";
    }

    return 0;
}