#include <fstream>
#include <cstdio>
#include <vector>

using namespace std;

FILE *fin = fopen ("ctc.in", "r");
ofstream fout ("ctc.out");

vector <int> G[100010], GT[100010], ctc[100010];
int n, m, i, j;
int x, y;
int viz[100010], postordine[100010], unde[100010];

void DFS (int x)
{
    int i;
    viz[x] = 1;
    for (i = 0; i < G[x].size(); i++)
        if (viz[G[x][i]] == 0)
            DFS (G[x][i]);
    postordine[++postordine[0]] = x;
}

void DFST (int x, int nr_ctc)
{
    int i;
    unde[x] = nr_ctc;
    ctc[nr_ctc].push_back (x);
    for (i = 0; i < GT[x].size(); i++)
        if (unde[GT[x][i]] == 0)
            DFST (GT[x][i], nr_ctc);
}

int main()
{
    fscanf (fin, "%d %d", &n, &m);
    for (i = 1; i <= m; i++)
    {
        fscanf (fin, "%d %d", &x, &y);
        G[x].push_back (y);
        GT[y].push_back (x);
    }

    for (i = 1; i <= n; i++)
        if (viz[i] == 0) DFS (i);

    int nr_ctc = 0;
    for (i = 1; i <= n; i++)
    {
        if (unde[i] == 0)
        {
            ++nr_ctc;
            DFST (i, nr_ctc);
        }
    }

    fout << nr_ctc << '\n';
    for (i = 1; i <= nr_ctc; i++)
    {
        for (j = 0; j < ctc[i].size(); j++) fout << ctc[i][j] << ' ';
        fout << '\n';
    }
    return 0;
}