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

#define MAXN 50050

typedef vector<int>::iterator iter;
typedef vector<int>::reverse_iterator riter;

int n, m;
vector<int> g[MAXN], gt[MAXN];
vector<int> order;
bitset<MAXN> viz;
vector<int> comp;
vector<vector<int> > comps;

void topo(int i)
{
    if (viz[i]) {
        return;
    }

    viz[i] = true;

    for (iter it = g[i].begin(); it != g[i].end(); ++it) {
        topo(*it);
    }

    order.push_back(i);
}

void conex(int i)
{
    if (viz[i]) {
        return;
    }

    viz[i] = true;

    comp.push_back(i);
    for (iter it = gt[i].begin(); it != gt[i].end(); ++it) {
        conex(*it);
    }
}

int main()
{
    fstream fin("ctc.in", ios::in);
    fstream fout("ctc.out", ios::out);

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

    for (int i = 1; i <= n; ++i) {
        topo(i);
    }

    viz.reset();
    for (riter it = order.rbegin(); it != order.rend(); ++it) {
        if (!viz[*it]) {
            conex(*it);
            comps.push_back(comp);
            comp.clear();
        }
    }

    fout << comps.size() << '\n';
    for (int i = 0; i < comps.size(); ++i) {
        for (iter it = comps[i].begin(); it != comps[i].end(); ++it) {
            fout << *it << " ";
        }
        fout << '\n';
    }

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