#include <cstdio>
#include <vector>
#include <cstring>
using namespace std;
const int nmax=1e5+3;
int viz[nmax],usu[nmax],nr,n,m,a,b,nod;
vector <int> v1[nmax],v2[nmax],sol[nmax];
void dfs1(int nod)
{
      usu[nod]=1;
      for(int i=0;i<v2[nod].size();++i)
      {
            if(!usu[v2[nod][i]]) dfs1(v2[nod][i]);
      }
}
void dfs2(int nod)
{
      if(usu[nod]==1)
      {
            ++usu[nod];
            viz[nod]=1;
            sol[nr].push_back(nod);
      }
      for(int i=0;i<v1[nod].size();++i)
      {
            if(usu[v1[nod][i]]==1) dfs2(v1[nod][i]);
      }
}
int main()
{
      freopen("ctc.in","r",stdin);
      freopen("ctc.out","w",stdout);
      scanf("%d%d",&n,&m);
      for(int i=1;i<=m;++i)
      {
            scanf("%d%d",&a,&b);
            v1[a].push_back(b);
            v2[b].push_back(a);
      }
      for(int i=1;i<=n;++i)
      {
            memset(usu,0,sizeof(usu));
            if(!viz[i])
            {
                  ++nr;
                  dfs1(i);
                  dfs2(i);
            }
      }
      printf("%d\n",nr);
      for(int i=1;i<=nr;++i)
      {
            for(int j=0;j<sol[i].size();++j) printf("%d ",sol[i][j]);
            printf("\n");
      }
      return 0;
}