#include <iostream>
#include <vector>
#include <fstream>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

const int NMAX = 100001;

int N, M, nrc;

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

bool viz[NMAX];

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

void afisare()
{
    g << nrc << '\n';
    for(int i = 1; i <= nrc; i++)
    {
        for(int x : CTC[i])
            g << x << ' ';
        g << '\n';
    }
}

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]);
        }
}

int main()
{
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}