#include <bits/stdc++.h>
#define Nmax 100000

using namespace std;

bool onStack[Nmax];
int d[Nmax];
int l[Nmax];
int ind=1;
stack <int> s;
vector <int> G[Nmax];
vector <int> comp[Nmax];
int k;


void tare_conexe(int node){
  d[node]=ind;
  l[node]=ind;
  ind++;
  s.push(node);
  onStack[node]=true;
  for(int i=0;i<G[node].size();i++){
    int dest=G[node][i];
    if(d[dest]==0){
      tare_conexe(dest);
      l[node]=min(l[node],l[dest]);
    }else if(onStack[dest]){
      l[node]=min(l[node],d[dest]);
    }
  }
  if(d[node]==l[node]){
    int dest=s.top();
    while(dest!=node){
      s.pop();
      onStack[dest]=false;
      comp[k].push_back(dest);
      dest=s.top();
    }
    s.pop();
    comp[k].push_back(node);
    k++;
  }
}

int main()
{
    FILE *fin, *fout;
    int n,m,i,j;
    fin=fopen("ctc.in","r");
    fout=fopen("ctc.out","w");
    fscanf(fin,"%d%d",&n,&m);
    for(m;m>0;m--){
      fscanf(fin,"%d%d",&i,&j);
      G[i].push_back(j);
    }
    for(i=1;i<=n;i++){
      if(d[i]==0){
        tare_conexe(i);
      }
    }
    fprintf(fout,"%d\n",k);
    for(i=0;i<k;i++){
      for(j=0;j<comp[i].size();j++){
        fprintf(fout,"%d ",comp[i][j]);
      }
      fprintf(fout,"\n");
    }
    fclose(fin);
    fclose(fout);
    return 0;
}