#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define N 100000
#define M 200000

typedef struct
{
    int vf, urm;
} element;

element succ[M+1], pred[M+1], ctc[N+1];
int lst_s[N+1], lst_p[N+1], lst_ctc[N+1], nr_s, nr_p, nr_ctc;
int sort_top[N+1], n_s_t;
bool viz[N+1];

void adauga_s(int x, int y)
{
    ++nr_s;
    succ[nr_s].vf = y;
    succ[nr_s].urm = lst_s[x];
    lst_s[x] = nr_s;
}

void adauga_p(int x, int y)
{
    ++nr_p;
    pred[nr_p].vf = y;
    pred[nr_p].urm = lst_p[x];
    lst_p[x] = nr_p;
}

void dfs(int x)
{
    viz[x] = true;
    for (int p = lst_s[x]; p != 0; p = succ[p].urm)
    {
        int y = succ[p].vf;
        if (!viz[y])
        {
            dfs(y);
        }
    }
    sort_top[++n_s_t] = x;
}

void dfs_t(int x, int n_ctc)
{
    viz[x] = true;
    nr_ctc++;
    ctc[nr_ctc].vf = x;
    ctc[nr_ctc].urm = lst_ctc[n_ctc];
    lst_ctc[n_ctc] = nr_ctc;
    for (int p = lst_p[x]; p != 0; p = pred[p].urm)
    {
        int y = pred[p].vf;
        if (!viz[y])
        {
            dfs_t(y, n_ctc);
        }
    }
}

int main()
{
    FILE *in, *out;
    in = fopen("ctc.in", "r");
    out = fopen("ctc.out", "w");
    int n, m;
    fscanf(in, "%d%d", &n, &m);
    for (int i = 0; i < m; i++)
    {
        int x, y;
        fscanf(in, "%d%d", &x, &y);
        adauga_s(x, y);
        adauga_p(y, x);
    }
    for (int i = 1; i <= n; i++)
    {
        if (!viz[i])
        {
            dfs(i);
        }
    }
    for (int i = 1; i <= n; i++)
    {
        viz[i] = false;
    }
    int n_ctc = 0;
    for (int i = n_s_t; i >= 1; i--)
    {
        int x = sort_top[i];
        if (!viz[x])
        {
            ++n_ctc;
            dfs_t(x, n_ctc);
        }
    }
    fprintf(out, "%d\n", n_ctc);
    for (int i = 1; i <= n_ctc; i++)
    {
        ///afisam varfurile din ctc cu numarul i
        for (int p = lst_ctc[i]; p != 0; p = ctc[p].urm)
        {
            fprintf(out, "%d ", ctc[p].vf);
        }
        fprintf(out, "\n");
    }
    fclose(in);
    fclose(out);
    return 0;
}