# include <stdio.h>
int s[100001],i,j,n,m,k,x,y,x1,x2,q,w,d[100001];
struct nod
{
int info;
nod *urm;
}*a[100001],*b[100001],*p,*v,*c[100001];

void df (int x)
{
nod *p;
p=a[x];
s[x]=1;
while (p)
{
if (s[p->info]==0)
{
df(p->info);
w++;
d[w]=p->info;
}
p=p->urm;
}
}

void df2 (int x)
{
nod *p;
s[x]=0;
p=b[x];
v=new nod;
v->info=x;
v->urm=c[k];
c[k]=v;
while (p)
{
if (s[p->info]==1)
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)
{
df (i);
w++;
d[w]=i;

}
for (j=n;j>=1;j--)
if (s[d[j]]==1)
{
k++;
df2(d[j]);
}


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;

}