#include <iostream>
#include <fstream>
#include <vector>
#define nl '\n'

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int NMAX = 1e5+1;

int N, M, nrc;

vector<int> G[NMAX], GT[NMAX],
        CTC[NMAX],
        Post;
bool viz[NMAX];

void citire()
{
    int x, y;
    fin >> N >> M;
    while (M--)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int vf)
{
    viz[vf] = 1;
    for (int x : G[vf])
        if (viz[x] == 0)
            dfs(x);
    Post.push_back(vf);
}

void dfsGT(int vf)
{
    viz[vf] = 0;
    CTC[nrc].push_back(vf);
    for (int x : GT[vf])
        if (viz[x] == 1)
            dfsGT(x);
}

void componente()
{
    int i;
    for (i = 1; i <= N; i++)
        if (viz[i] == 0)
            dfs(i);
    for (i = Post.size() - 1; i >= 0; i--)
    {
        if (viz[Post[i]] == 1)
        {
            nrc++;
            dfsGT(Post[i]);
        }
    }
}

void afisare()
{
    fout << nrc << nl;
    for (int i = 1; i <= nrc; i++)
    {
        for (int x : CTC[i])
            fout << x << ' ';
        fout << nl;
    }
}
int main()
{
    citire();
    componente();
    afisare();
    return 0;
}