#include<iostream.h>
#include<fstream.h>
#include<stdlib.h>
#define N 100001
#define M 200001
typedef struct stack
{long st[N],sp;};
stack s;
long n,m,a[M],b[M],deg[N]={0},*g[N],k,i,j,t,ind,c[N]={0},l[N]={0},nr,p,e[N],*d[N];

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 j,r;
c[i]=ind;
l[i]=ind;
ind++;
if(apartine(s,i)==0)
       push(s,i);
for(j=deg[i]-1;j>=0;j--)
if(c[g[i][j]]==0)
       {tarjan(g[i][j]);
       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++;
       k=0;
       d[nr]=(long*)malloc((s.sp+1)*sizeof(long));
       if(s.sp!=0)
              {while(s.sp!=0)
                      d[nr][++k]=pop(s);
              e[nr]=k;}
       else
              {d[nr][1]=i;
              e[nr]=1;}}}

int main()
{ifstream f1("ctc.in");
ofstream f2("ctc.out");
f1>>n>>m;
for(k=1;k<=m;k++)
       {f1>>a[k]>>b[k];
       deg[b[k]]++;}
for(i=1;i<=n;i++)
       {g[i]=(long*)malloc(deg[i]*sizeof(long));
       deg[i]=0;}
for(j=1;j<=m;j++)
       g[b[j]][deg[b[j]]++]=a[j];
nr=0;
ind=0;
s.sp=0;
for(i=1;i<=n;i++)
if(c[i]==0)
       tarjan(i);
f2<<nr<<endl;
for(j=1;j<=nr;j++)
       {for(k=e[j];k>=1;k--)
             f2<<d[j][k]<<" ";
       f2<<endl;}
f1.close();
f2.close();
return 0;}