#include <fstream>
#include <vector>
#include <bitset>

using namespace std;

const int N = 1e5;

vector <int> succesori[N+1], predecesori[N+1];
vector <vector <int>> ctc;
vector <int> s;
bitset <N+1> viz;
int n;

void dfs(int x)
{
    viz[x] = 1;
    for (auto y: succesori[x])
    {
        if (!viz[y])
        {
            dfs(y);
        }
    }
    s.push_back(x);
}

void dfs_t(int x)
{
    ctc[ctc.size()-1].push_back(x);
    viz[x] = 1;
    for (auto y: predecesori[x])
    {
        if (!viz[y])
        {
            dfs_t(y);
        }
    }
}

int main()
{
    ifstream in("ctc.in");
    ofstream out("ctc.out");
    int m;
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x, y;
        in >> x >> y;
        succesori[x].push_back(y);
        predecesori[y].push_back(x);
    }
    in.close();
    ///construim vectorul s (la fel ca la sortarea topologica cu dfs)
    for (int i = 1; i <= n; i++)
    {
        if (!viz[i])
        {
            dfs(i);
        }
    }
    ///trecem la etapa a doua: parcurgeri ale gr. transpus in ordinea inversa a lui s
    viz.reset();///resetam elementele lui viz la valoarea 0
    for (int i = (int)s.size() - 1; i >= 0; i--)
    {
        if (!viz[s[i]])
        {
            vector <int> aux;
            ctc.push_back(aux);
            dfs_t(s[i]);///dfs in graful transpus
        }
    }
    ///afisez "matricea" ctc
    out << ctc.size() << "\n";
    for (int i = 0; i < (int)ctc.size(); i++)
    {
        ///afisez varfurile din componenta i:
        for (auto x: ctc[i])
        {
            out << x << " ";
        }
        out << "\n";
    }
    out.close();
    return 0;
}