#include <iostream>
#include <fstream>
using namespace std;
 
ifstream fin("ctc.in");
ofstream fout("ctc.out");
 
struct Nod{int inf; Nod* leg;};
typedef Nod* nod;
 
nod a[100001],b[100001],c[100002];
 
int n,m,s[100001], viz[100001],viz2[100001],k;

void afisare(nod q)
{
	for(;q;q=q->leg) fout<<q->inf<<" ";
	fout<<endl;
}
 
void adaug(nod &q, int x)
{
    nod p=new Nod;
    p->inf=x;
    p->leg=q;
    q=p;
}

adaug2(int s[], int i)
{
	t++;
	s[t]=i;
}
 
void parc(int i)
{
	nod j;
    viz[i]=1;
    for(j=a[i]; j; j=j->leg) 
       if (!viz[j->inf])
         parc(j->inf);
	adaug2(s,i);
}
 
void parc2(int i)
{
    viz2[i]=k;
	adaug(c[k],i);
    for(nod j=b[i]; j; j=j->leg) if (!viz2[j->inf]) parc2(j->inf);
}
 
int main()
{
    int i,j,x,y;
    fin>>n>>m;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y;
        adaug(a[x],y);
        adaug(b[y],x);
    }
    for(i=n; i>=1; i--)
        if(!viz[i])
            parc(i);
	while(t)
	{
		if (!viz2[s[t]])
		{
			k++;
			parc2(s[t]);
		} 
		t--;
	}
    fout<<k<<"\n";
    for(i=1; i<=k; i++)
       afisare(c[i]);

    return 0;
}