#include <fstream>
#include <vector>

using namespace std;

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

const int Nmax = 100005;

vector<int> A[Nmax];
vector<int> T[Nmax];

void DFS (int nod, vector<bool>&viz, vector<int>&postordine)
{
    viz[nod] = 1;
    for (auto i = 0; i < A[nod].size(); i++)
    {
        int nod_curent = A[nod][i];
        if (!viz[nod_curent])
            DFS(nod_curent, viz, postordine);
    }
    postordine.push_back(nod);
}

void DFST (int nod, int cnt, vector<bool>&viz, vector<vector<int> >&grup)
{
    viz[nod] = 0;
    grup[cnt].push_back(nod);
    for (auto i = 0; i < T[nod].size(); i++)
    {
        int nod_curent = T[nod][i];
        if (viz[nod_curent])
            DFST(nod_curent, cnt, viz, grup);
    }
}

int main()
{
    int n, m, cnt = 0;
    in >> n >> m;

    vector<bool> viz(n + 1);
    vector<int> postordine;
    vector<vector<int> > grup(n + 1, vector<int>());

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;

        A[x].push_back(y);
        T[y].push_back(x);
    }

    for (int i = 1; i <= n; i++)
        if (!viz[i])
            DFS(i, viz, postordine);

    for (int i = n - 1; i >= 0; i--)
        if (viz[postordine[i]])
            cnt++, DFST(postordine[i], cnt, viz, grup);

    out << cnt << '\n';
    for (int i = 1; i <= cnt; i++)
    {
        for (int j = 0; j < grup[i].size(); j++)
            out << grup[i][j] << ' ';
        out << '\n';
    }

    return 0;
}