#include <iostream>
#include <fstream>
using namespace std;
struct nod{int x;nod* urm;};
nod *L[100001],*LT[100001];
int n,m,s[100001],ns,u[100001],nr;
void Adauga_Leg(nod*& p, int x)
{
    nod* c = new nod;
    c->x=x;
    c->urm=p;
    p=c;
}
void Citeste()
{
    ifstream f("ctc.in");
    f>>n>>m;
    int x,y;
    while(f>>x>>y)
    {
        Adauga_Leg(L[x],y);
        Adauga_Leg(LT[y],x);
    }
    f.close();
}
void DF1(int x)
{
    u[x]=1;
    for(nod* c=L[x];c;c=c->urm)
        if(!u[c->x]) DF1(c->x);
    s[ns++] = x;
}
void DF2 (int x, int k)
{
    u[x]=k;
    for(nod* c=LT[x];c;c=c->urm)
        if(!u[c->x]) DF2(c->x,k);
}
void Scrie()
{
    ofstream g("ctc.out");
    g<<nr<<endl;
    for(int i=1;i<=nr;i++)
    {
        for(int j=1;j<=n;j++)
            if(u[j]==i) g<<j<<" ";
        g<<endl;
    }
    g.close();
}
int main()
{
    Citeste();
    for(int i=1;i<=n;i++)
        if(!u[i]) DF1(i);
    for(int i=1;i<=n;i++)
        u[i]=0;
    for(int i=n-1;i>=0;i--)
        if(!u[s[i]])
        {
            nr++;
            DF2(s[i],nr);
        }
    Scrie();
    return 0;
}