#include <cstdio>
#include <stack>
using namespace std;
//ifstream fin("ctc.in");
//ofstream fout("ctc.out");

FILE *f=fopen("ctc.in","r");
FILE *gg=fopen("ctc.out","w");

struct nod
{ int info;
  nod*urm;
};

nod* g[100001];  bool viz[100001];
nod* gt[100001]; bool vizt[100001];
stack<int> S;
stack<int> ST;

int n,m;

inline void Add(nod *&prim,int x)
{ nod* p=new nod;
  p->info=x;
  p->urm=prim;
  prim=p;
}

void Citire()
{ int i,x,y;
  //fin>>n>>m;
  fscanf(f,"%d%d",&n,&m);
  for(i=1;i<=m;i++)
     {   //fin>>x>>y;
         fscanf(f,"%d%d",&x,&y);
         Add(g[x],y);
         Add(gt[y],x);
     }
}


void DFS(int x)
{ viz[x]=true;
  for(nod* p=g[x];p!=NULL;p=p->urm)
      if(viz[p->info]==false)
         DFS(p->info);
  S.push(x);
}

void DFST(int x)
{ vizt[x]=true;
  for(nod* p=gt[x];p!=NULL;p=p->urm)
      if(vizt[p->info]==false)
         DFST(p->info);
  ST.push(x);
}

int main()
{   Citire();
    int i,nr=0,x;
    for(i=1;i<=n;i++)
        if(viz[i]==false) DFS(i);
    while(!S.empty())
       { x=S.top(); S.pop();
         if(vizt[x]==false)
             {ST.push(-1);DFST(x); nr++;}
       }
    //fout<<nr<<"\n";
    fprintf(gg,"%d\n",nr);
    while (!ST.empty())
    { x=ST.top();
      if(x==-1) fprintf(gg,"\n");
      else fprintf(gg,"%d ",x);
      ST.pop();
    }
    fprintf(gg,"%f\n",(sizeof(g)*2+sizeof(viz)*2)/1024.0);
    return 0;
}