#include<stdio.h>
#include<stdlib.h>
#define N 100001
#define M 200001
typedef struct nod
{long info;
struct nod *leg;}Nod,*list;

typedef struct stack
{long st[N],sp;};

stack s;
list q=NULL;
long n,m,deg[N]={0},*g[N],k,i,j,t,ind,c[N]={0},l[N],nr,a[M],b[M],u,v[N]={0};

void add(list &q,long x)
{Nod *p=new Nod;
p->info=x;
p->leg=q;
q=p;}

int contine(list &q,long x)
{Nod *p;
for(p=q;p!=NULL;p=p->leg)
if(p->info==x)
      return 1;
return 0;}

long del(list &q)
{Nod *p=q->leg;
long x=q->info;
free(q);
q=p;
return x;}

void push(stack &s,long x)
{s.st[++s.sp]=x;}

long pop(stack &s)
{return s.st[s.sp--];}

int apartine(stack &s,long x)
{long i;
for(i=1;i<=s.sp;i++)
if(s.st[i]==x)
      return 1;
return 0;}

void tarjan(long i,long *nr,long *ind)
{long j,r;
push(s,i);
c[i]=(*ind);
l[i]=(*ind)++;
for(j=0;j<deg[i];j++)
if(c[g[i][j]]==0)
       {tarjan(g[i][j],nr,ind);
       if(l[i]>l[g[i][j]])
              l[i]=l[g[i][j]];}
else
       if(apartine(s,g[i][j])==1&&l[i]>c[g[i][j]])
              l[i]=c[g[i][j]];
if(c[i]==l[i])
       {(*nr)++;
       while(s.sp!=0)
             {r=pop(s);
             if(contine(q,r)==0)
                    if(r!=i)
                            {add(q,r);
                            printf("%ld ",r);}
                    else
                            break;
             else
                    break;}
       if(contine(q,i)==0)
             {add(q,i);
             printf("%ld ",i);}
       r=del(q);
       if(r==0)
             (*nr)--;
       else
             {add(q,r);
             printf("\n");}
       add(q,0);}}

int main()
{freopen("ctc.in","r",stdin);
freopen("ctc.out","w",stdout);
scanf("%ld%ld\n",&n,&m);
for(k=1;k<=m;k++)
       {scanf("%ld%ld\n",&a[k],&b[k]);
       deg[a[k]]++;}
for(i=1;i<=n;deg[i++]=0)
       g[i]=(long*)malloc(deg[i]*sizeof(long));
for(j=1;j<=m;j++)
       g[a[j]][deg[a[j]]++]=b[j];
ind=0;
nr=0;
s.sp=0;
add(q,0);
printf("\n");
for(u=1;u<=n;u++)
if(c[u]==0)
       tarjan(u,&nr,&ind);
fseek(stdout,0,SEEK_SET);
printf("%ld",nr);
fclose(stdin);
fclose(stdout);
return 0;}