/*#include <iostream>
#include <fstream>
#include <vector>


using namespace std;
const int NMAX = 100001;

int N, M, nrc;

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

bool viz[NMAX];

ifstream f("ctc.in");
ofstream g("ctc.out");

void citire()
{
    int x, y;
    f >> N >> M;

    while(M--)
    {
        f >> 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()
{
    g << nrc << '\n';
    for(int i = 1; i <= nrc; ++i)
    {

        for(int x : CTC[i])
            g << x << ' ';
        g << '\n';
    }
}

int main()
{
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}
V2-liste simplu inlantuite*/
#include <iostream>
#include <fstream>

using namespace std;
const int NMAX = 100001;

struct nod
{
    int x;
    nod *next;
};

int N, M,
    post[NMAX], nr,
    nrc;
bool viz[NMAX];

nod *G[NMAX], *GT[NMAX],
    *CTC[NMAX];

ifstream f("ctc.in");
ofstream g("ctc.out");

void add(nod *&cap_lst, int nod_ad)
{
    nod *p = new nod;
    p->x = nod_ad;
    p->next = cap_lst;
    cap_lst = p;
}

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

void DFS(int vf)
{
    viz[vf] = 1;
    for (nod *p = G[vf]; p != NULL; p = p -> next)
        if (!viz[p -> x])
            DFS(p -> x);
    post[++nr] = vf;
}

void DFSt(int vf)
{
    viz[vf] = 0;
    add(CTC[nrc], vf);
    for (nod *p = GT[vf]; p != NULL; p = p -> next)
        if (viz[p -> x])
            DFSt(p -> x);
}

void componente()
{
    int i;
    for (i = 1; i <= N; i++)
        if (!viz[i])
            DFS(i);
    for (i = N; i >= 1; i--)
        if (viz[post[i]])
        {
            nrc++;
            DFSt(post[i]);
        }
}

void afisare()
{
    g << nrc << '\n';
    for (int i = 1; i <= nrc; i++)
    {
        for (nod *p = CTC[i]; p != NULL; p = p->next)
            g << p->x << ' ';
        g << '\n';
    }
}

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