#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#define MAXN 100005
#define MAXM 200005
#define ALB 0
#define GRI 1
#define BLK 2
using namespace std;

vector <int> graf[MAXN];
vector <int> ginv[MAXN];
vector <int> ans[MAXN];
vector <int> parc;

int seen[MAXN];

void DFS(int node,vector <int> *grf,vector <int> *dat){
  seen[node]=1;
  for(int neigh : grf[node]){
    if(seen[neigh]==0){
      DFS(neigh,grf,dat);
    }
  }
  (*dat).push_back(node);
}

int main(){
  int n,m,i,x,y;
  FILE *fin,*fout;
  fin=fopen("ctc.in","r");
  fout=fopen("ctc.out","w");
  fscanf(fin,"%d%d",&n,&m);

  for(i=0;i<m;i++){
    fscanf(fin,"%d%d",&x,&y);
    graf[x].push_back(y);
    ginv[y].push_back(x);
  }

  for(i=1;i<=n;i++){
    if(seen[i]==0){
      DFS(i,graf,&parc);
    }
  }

  for(i=1;i<=n;i++){
    seen[i]=0;
  }

  int r=0;
  while(!parc.empty()){
    int elem=parc.back();
    parc.pop_back();
    if(seen[elem]==0){
      DFS(elem,ginv,&ans[r]);
      r++;
    }
  }

  fprintf(fout,"%d\n",r);
  for(i=0;i<r;i++){
    for(int node : ans[i]){
      fprintf(fout,"%d ",node);
    }
    fprintf(fout,"\n");
  }


  fclose(fin);
  fclose(fout);
  return 0;
}