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#include<cstdio>
#include<vector>
const int N=100001;
vector<int> s[N];
int n,m,a[N],c,r,*u[N],*v[N],w[N],z[N],x[2*N],y[2*N],i,j;
bool b[N];
void A(int i)
{
if(b[i])
return;
int j;
for(b[i]=1,j=0;j<w[i];j++)
A(u[i][j]);
a[++c]=i;
}
void B(int i)
{
if(!b[i])
return;
int j;
for(b[i]=j=0;j<z[i];j++)
B(v[i][j]);
s[r].push_back(i);
}
int main()
{
freopen("ctc.in","r",stdin),freopen("ctc.out","w",stdout),scanf("%d%d",&n,&m);
for(i=0;i<m;i++)
scanf("%d%d",x+i,y+i),w[x[i]]++,z[y[i]]++;
for(i=1;i<=n;i++)
u[i]=new int[w[i]],v[i]=new int[z[i]],w[i]=z[i]=0;
for(i=0;i<m;i++)
u[x[i]][w[x[i]]++]=y[i],v[y[i]][z[y[i]]++]=x[i];
for(i=1;i<=n;i++)
A(i);
for(i=n;i;i--)
if(b[a[i]])
r++,B(a[i]);
for(printf("%d\n",r),i=r;i;i--)
{
for(c=s[i].size(),j=0;j<c;j++)
printf("%d ",s[i][j]);
printf("\n");
}
}