#include <stdio.h>
#include <vector>
using namespace std;
#define nmax 100001
vector<int> v,g[nmax],gt[nmax],sol[nmax];
bool viz[nmax],viz2[nmax];
long n,nr,nrc;
void read()
 {
 FILE *f=fopen("ctc.in","r");
 long m,x,y;
 fscanf(f,"%ld %ld",&n,&m);
 for(int i=1;i<=m;i++)
  {
  fscanf(f,"%ld %ld",&x,&y);
  //f>>x>>y;
  g[x].push_back(y);
  gt[y].push_back(x);
  }
 }
void dfs(int x)
 {
 viz[x]=1;
 v.push_back(x);
 for(int i=0;i<g[x].size();i++)
  if(!viz[g[x][i]])
   dfs(g[x][i]);
 }
void dfs2(int x)
 {
 viz2[x]=1;
 sol[nrc].push_back(x);
 for(int i=0;i<gt[x].size();i++)
  if(viz[gt[x][i]]&&!viz2[gt[x][i]])
   dfs2(gt[x][i]);
 }
void solve()
 {
 for(int i=1;i<=n;i++)
  if(!viz[i])
   {
   dfs(i);
   nr=v.size();
   for(int j=0;j<nr;j++)
    {
    if(!viz2[v[j]])
     {
     nrc++;
     dfs2(v[j]);
     }
    }
   }
 }
void show()
 {
 FILE *g=fopen("ctc.out","w");
 int i,j;
 fprintf(g,"%ld\n",nrc);
 //g<<nrc<<endl;
 for(i=1;i<=nrc;i++)
  {
  for(j=0;j<sol[i].size();j++)
   fprintf(g,"%ld ",sol[i][j]);
   //g<<sol[i][j]<<" ";
  fprintf(g,"\n");
  }
 }
int main()
 {
 read();
 solve();
 show();
 return 0;
 }