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

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

int main()
{freopen("ctc.in","r",stdin);
freopen("ctc.out","w",stdout);
scanf("%ld%ld",&n,&m);
for(k=1;k<=m;k++)
       {scanf("%ld%ld",&a[k],&b[k]);
       deg[a[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[a[j]][deg[a[j]]++]=b[j];
index=0;
nr=0;
s.sp=0;
q.sp=0;
for(i=1;i<=n;i++)
if(c[i]==0)
       tarjan(i,&nr,&index);
printf("%ld\n",nr);
for(j=1;j<=nr;j++)
       {for(k=1;k<=e[j];k++)
              printf("%ld ",d[j][k]);
       free(d[j]);
       printf("\n");}
fclose(stdin);
fclose(stdout);
return 0;}