#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int>M[NMAX];
vector<int>T[NMAX];
int n,m,lg;
int postordine[NMAX];
bool uz[NMAX];
int ctc[NMAX],nrc=0; //ctc[i]=componenta tare conexa din care face parte varful i

void dfs1(int x);
void dfs2(int x);
void citire();
int main()
{int i,j;
 citire();
 for(i=1;i<=n;i++)
     if(!uz[i])
       dfs1(i);
 for(i=1;i<=n;i++)
    uz[i]=0;
 for(i=n;i>=1;i--)
   if(!uz[postordine[i]])
     {dfs2(postordine[i]);
      nrc++;
     }
 fout<<nrc<<'\n';
 for(i=0;i<=nrc;i++)
    {for(j=1;j<=n;j++)
       if(ctc[j]==i)
         fout<<j<<' ';
     fout<<'\n';
    }
 return 0;
}
void citire()
{int i,x,y;
 fin>>n>>m;
 for(i=1;i<=m;i++)
    {fin>>x>>y;
     M[x].push_back(y);
     T[y].push_back(x);
    }
}
void dfs1(int x)
{int i;
 for(i=0;i<M[x].size();i++)
    if(!uz[M[x][i]])
      {uz[M[x][i]]=1;
       dfs1(M[x][i]);
      }
 postordine[lg]=x;
 lg++;
}
void dfs2(int x)
{int i;
 ctc[x]=nrc;
 for(i=0;i<T[x].size();i++)
   if(!uz[T[x][i]])
     {uz[T[x][i]]=1;
      dfs2(T[x][i]);
     }

}