#include<stdio.h>
#include<stdlib.h>
#define NMAX 100003
typedef struct Node{int info; struct Node *next;}Node;
Node *G[NMAX];
FILE *inf,*outf;
int viz[NMAX],N,M;


void citire()
{
inf=fopen("ctc.in","r");
int i,z,y;
fscanf(inf,"%d %d",&N,&M);
for(i=1;i<=M;i++)
 {
  fscanf(inf,"%d %d",&z,&y);
  Node *p;
  if(!(p=(Node*)malloc(sizeof(Node)))) return ;
  p->info=y;
  p->next=G[z];
  G[z]=p;
 }
}

void Dfs(int x,int contor)
{
Node *p;
viz[x]=contor;
for(p=G[x];p;p=p->next)
      if(viz[p->info]==0)
      {
      Dfs(p->info,contor);
      }     
}


int main()
{
int i,contor=0,k;

outf=fopen("ctc.out","w");
citire();

for(i=1;i<=N;i++)
    if(viz[i]==0) {  Dfs(i,++contor); }
fprintf(outf,"%d\n",contor);
for(k=1;k<=contor;k++)
{
for(i=1;i<=N;i++) 
   if(viz[i]==k) fprintf(outf,"%d ",i);
fprintf(outf,"\n");
}
fclose(inf);
fclose(outf);
return 0;    
}