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

#define MAXN 100005

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

FILE* f = fopen("ctc.in", "r");
FILE* g = fopen("ctc.out", "w");

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] == true) {
        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] == true) {
        return;
    }
    viz[i] = true;

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

int main()
{
    fscanf(f, "%d %d\n", &n, &m);
    for (int i = 1; i <= m; i++) {
        int x, y;
        fscanf(f, "%d %d\n", &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] == false) {
            conex(*it);
            comps.push_back(comp);
            comp.clear();
        }
    }

    fprintf(g, "%d\n", comps.size());
    for (int i = 0; i < comps.size(); i++) {
        for (iter it = comps[i].begin(); it != comps[i].end(); it++) {
            fprintf(g, "%d ", *it);
        }
        fprintf(g, "\n");
    }

    fclose(f);
    fclose(g);
}