#include <iostream>
#include <fstream>
#include <vector>
#include <string.h>
using namespace std;

#define NMAX 100001

vector <int> v[NMAX], vt[NMAX], ctc[NMAX];
int viz[NMAX], p[NMAX], nr;

void dfs(int nod) {
    viz[nod] = 1;
    for (vector <int> :: iterator it = v[nod].begin(); it != v[nod].end(); it++)
        if (viz[*it] == 0)
            dfs(*it);
    p[++p[0]] = nod;
}

void dfst(int nod) {
    viz[nod] = 1;
    ctc[nr].push_back(nod);
    for (vector <int> :: iterator it = vt[nod].begin(); it != vt[nod].end(); it++)
        if (viz[*it] == 0)
            dfst(*it);
}

int main()
{
    int n, m, i, x, y;
    ifstream f("ctc.in");
    ofstream g("ctc.out");
    f >> n >> m;
    for (i = 1; i <= m; i++) {
        f >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    f.close();
    for (i = 1; i <= n; i++)
        if (viz[i] == 0)
            dfs(i);
    nr = 0;
    memset(viz, 0, sizeof(viz));
    for (i = n; i >= 1; i--)
        if (viz[p[i]] == 0) {
            nr++;
            dfst(p[i]);
        }
    g << nr << '\n';
    for (i = 1; i <= nr; i++) {
        for (vector <int> :: iterator it = ctc[i].begin(); it != ctc[i].end(); it++)
            g << *it << " ";
        g << '\n';
    }
    g.close();
    return 0;
}