#include <fstream>
#include <vector>
#include <set>
#define nmax 100000+5
using namespace std;

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

vector<int> graf[nmax];
vector<int> grafTranspus[nmax];
vector<int> postOrdine;
vector<set<int> > componente;
int n;
int u[nmax];
void citire()
{
    int m;
    int x, y;

    fin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        fin >> x >> y;

        graf[x].push_back(y);
        grafTranspus[y].push_back(x);
    }
}

void dfs(int curent)
{
    int vecin;
    u[curent] = 1;
    for (int i = 0; i < graf[curent].size(); i++)
    {
        vecin = graf[curent][i];
        if (!u[vecin])
            dfs(vecin);
    }
    postOrdine.push_back(curent);
}

void dfsTranspus(int curent)
{
    int vecin;
    u[curent] = 0;
    for (int i = 0; i < grafTranspus[curent].size(); i++)
    {
        vecin = grafTranspus[curent][i];
        if (u[vecin])
            dfsTranspus(vecin);
    }
    componente.back().insert(curent);
}

void rezolvare()
{
    for (int i = 1; i <= n; i++)
        if (!u[i])
            dfs(i);
    for (int i = postOrdine.size()-1; i >= 0; i--)
        if (u[postOrdine[i]])
        {
            componente.push_back(set<int>());
            dfsTranspus(postOrdine[i]);
        }
}

void afisare()
{
    fout << componente.size() << '\n';
    for (int i = 0; i < componente.size(); i++)
    {
        for (set<int>::iterator it = componente[i].begin(); it != componente[i].end(); it++)
            fout << *it << ' ';
        fout << '\n';
    }
}

int main()
{
    citire();
    rezolvare();
    afisare();
    return 0;
}