#include<stdio.h>
#include<stdlib.h>
#define N 100001
#define M 200001
typedef struct stack
{long st[N],sp;};

stack s;
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 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)++;
       if(s.sp!=0)
              {if(*nr==1)
                   {printf("%ld ",i);
                   v[i]=apartine(s,i);}
              while(s.sp!=0)
                   {r=pop(s);
                   if(v[r]==0)
                          printf("%ld ",r);
                   v[r]=apartine(s,r);
                   if(r==i)
                          break;}
              printf("\n");}
       else
              (*nr)--;}}

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;
printf("\n");
for(u=1;u<=n;u++)
if(c[u]==0)
       tarjan(u,&nr,&ind);
fseek(stdout,0,SEEK_SET);
printf("%ld\n",nr);
fclose(stdin);
fclose(stdout);
return 0;}