# include <stdio.h>
int s[100001],s1[100001],s2[100001],i,j,n,m,k,x,y;
struct nod
{
int info;
nod *urm;
}*a[100001],*b[100001],*p,*v,*c[100001];
void df1 (int x)
{
nod *p;
p=a[x];
s1[x]=1;
while (p)
{
if (s1[p->info]==0)
df1 (p->info);
p=p->urm;
}
}

void df2 (int x)
{
nod *p;
p=b[x];
s2[x]=1;
while (p)
{
if (s2[p->info]==0)
df2 (p->info);
p=p->urm;
}
}



int main ()
{
freopen ("ctc.in","r",stdin);
freopen ("ctc.out","w",stdout);
scanf ("%i%i",&n,&m);
for (i=1;i<=m;i++)
{
scanf ("%i%i",&x,&y);

p=new nod;
p->info=y;
p->urm=a[x];
a[x]=p;

p=new nod;
p->info=x;
p->urm=b[y];
b[y]=p;
}


for (i=1;i<=n;i++)
if (s[i]==0)
{
df1 (i);
df2 (i);
k++;
for (j=1;j<=n;j++)
if (s[j]==0)
if (s1[j]==1 && s2[j]==1)
{
s[j]=1;
p=new nod;
p->info=j;
p->urm=c[k];
c[k]=p;
}
for (j=1;j<=n;j++)
s1[j]=s2[j]=0;
}


printf ("%i\n",k);

for (i=1;i<=k;i++)
{
while (c[i])
{
printf ("%i ",c[i]->info);
c[i]=c[i]->urm;
}
printf ("\n");
}
return 0;

}