#include <fstream>
#include <cstring>

using namespace std;

ifstream F("ctc.in");
ofstream G("ctc.out");

int v[100003], n, m, K = 1, k, w[100003], x, y;
struct node{int info; node *urm;} *L1[100003], *L[100002], *l[100003], *q;

void dfs(int nod)
{
    v[nod] = 1;
    node *p;
    p = L[nod]->urm;
    while(p != NULL)
    {
        if(!v[p->info]) dfs(p->info);
        p=p->urm;
    }
    w[++ k] = nod;
}

void dfs1(int nod)
{
    v[nod] = 1;
    node *p;
    p = L1[nod]->urm;
    while(p != NULL)
    {
        if(!v[p->info]) dfs1(p->info);
        p=p->urm;
    }
    q = new node;
    q->urm = l[K]->urm;
    q->info = nod;
    l[K]->urm = q;
}

int main()
{
    F >> n >> m;
    for(int i = 1; i <= n; ++ i)
        L[i] = new node, L[i]->urm = NULL;
    for(int i = 1; i <= n; ++ i)
        L1[i] = new node, L1[i]->urm = NULL;
    for(int i = 0; i < m; ++ i)
    {
        F >> x >> y;
        q = new node;
        q->urm = L[x]->urm;
        q->info = y;
        L[x]->urm = q;
        q = new node;
        q->urm = L1[y]->urm;
        q->info = x;
        L1[y]->urm = q;
    }
    for(int i = 1; i <= n; ++ i)
        if(!v[i]) dfs(i);
    for(int i = 1; i <= k; ++ i)
        l[i] = new node, l[i]->urm = NULL;
    memset(v, 0, sizeof(v));
    for(int i = k; i > 0; -- i)
        if(!v[w[i]])dfs1(w[i]), ++K;
    G << K - 1<< '\n';
    for(int i = 1; i < K; ++ i)
    {
        q = l[i]->urm;
        while(q != NULL)
        {
            G << q->info << " ";
            q=q->urm;
        }
        G << '\n';
    }
    return 0;
}