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