#include <iostream>
#include<fstream>
#include<vector>
#include<cstring>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> gr[100001], grt[100001];
int n,m,x,y,nr, st[100001], viz[100001],K;
vector <int> ct[100001];
void dfs(int k){
    viz[k]=1;
     for (auto i:gr[k])
          if(viz[i]==0)
              dfs(i);
     st[++K]=k;
 }
 void dfst(int k){
    viz[k]=1;
    ct[nr].push_back(k);
     for (auto i:grt[k])
          if(viz[i]==0)
              dfst(i);

 }
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        gr[x].push_back(y);
        grt[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
          if(viz[i]==0)
              dfs(i);
    memset(viz, 0, sizeof(viz));
    for(int i=n;i>=1;i--)
          if(viz[st[i]]==0){
               nr++;
               dfst(st[i]);

          }
      fout<<nr<<"\n";
      for(int i=1;i<=nr;i++)
      {
          for( auto j:ct[i])
               fout<<j<<" ";
          fout<<"\n";
      }
    return 0;
}