#define MAX_N 100000

#include <fstream>
#include <vector>
#include <bitset>
#include <algorithm>
#include <iostream>
using namespace std;

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

int n, m, M[MAX_N + 1];
int t, T[MAX_N + 1];
vector<int> G[MAX_N + 1], C[MAX_N + 1];

void Df(int nod);
int Urca(int x);

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

    for (int i = 1, x, y; i <= m; ++i)
    {
        fin >> x >> y;
        G[x].push_back(y);
    }

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

    int ctc = 0;
    for (int i = 1; i <= n; ++i)
    {
        int u = Urca(i);

        if (C[u].size() == 0) { ++ctc; }
        C[u].push_back(i);
    }

    fout << ctc << '\n';
    for (int i = 1; i <= n; ++i)
    {
        for (int nod : C[i])
        {
            fout << nod << ' ';
        }

        if (C[i].size() > 0)
        {
            fout << '\n';
        }
    }

    fin.close();
    fout.close();
    return 0;
}

void Df(int nod)
{
    M[nod] = nod;
    T[nod] = ++t;

    for (int vecin : G[nod])
    {
        if (T[vecin] == 0)
        {
            Df(vecin);
        }

        if (T[M[nod]] > T[M[vecin]])
        {
            M[nod] = M[vecin];
        }
    }
}

int Urca(int x)
{
    if (M[x] == x) { return x; }

    return M[x] = Urca(M[x]);
}