#include <iostream>
#include <fstream>

using namespace std;

const int N = 200001;
int n, m, nr, s, nc, q[N], distances[N], c[N];
int vf[2 * N], vf1[2 * N], lst[N], lst1[N], urm[2 * N], urm1[2 * N];
bool viz[N], viz1[N];
int st[N], st1[N];
int varf;

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

void adauga(int x, int y) {
 vf[++nr] = y;
 urm[nr] = lst[x];
 lst[x] = nr;
 vf1[nr] = x;
 urm1[nr] = lst1[y];
 lst1[y] = nr;
}

void dfs(int x) {

 viz[x] = true;
 int y;
 for (int p = lst[x]; p != 0; p = urm[p]) {
  y = vf[p];
  if (!viz[y]) dfs(y);
 }
 st[++varf] = x;
}

void dfs1(int x) {
 viz1[x] = true;
 c[nc]++;
 st1[++nr] = x;
 int y;
 for (int p = lst1[x]; p != 0; p = urm1[p]) {
  y = vf1[p];
  if (!viz1[y]) dfs1(y);
 }
}

struct comp {
 int x, y;
}v[N];


int main() {
 in >> n >> m;
 for (int i = 1; i <= m; i++) {
  in >> v[i].x >> v[i].y;
  adauga(v[i].x, v[i].y);
 }
 for (int i = 1; i <= n; i++)
  if (!viz[i]) dfs(i);
 nr = 0;
 for (int i = n; i >= 1; i--) {
  if (!viz1[st[i]]) {
   nc++;
   dfs1(st[i]);
  }
 }

 int a = 1;
 out << nc << '\n';
 for (int i = 1; i <= nc; i++) {
  for (int j = 1; j <= c[i]; j++)
   out << st1[a++] << ' ';
  out << '\n';
 }
 return 0;
}