#include <iostream>
#include <fstream>

using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

struct nod
{
    int y;
    nod* next;
}*a[100005],*trans[100005],*rez[100005];

bool viz1[100005],viz2[100005];
int steve[100005],k,nr;

void dfs1(int idnod)
{
    viz1[idnod]=true;
    nod* i=a[idnod];
    while(i!=NULL)
    {
        if (viz1[i->y]==false)
            dfs1(i->y);
        i=i->next;
    }
    steve[k++]=idnod;
}

void dfs2(int idnod)
{
    ///afisare
    nod* nou=new nod;
    nou->y=idnod;
    nou->next=rez[nr];
    rez[nr]=nou;
    //
    viz2[idnod]=true;
    //k--;
    nod* i=trans[idnod];
    while(i!=NULL)
    {
        if (viz2[i->y]==false)
            dfs2(i->y);
        i=i->next;
    }
}

int main()
{
    int n,m;
    fin>>n>>m;
    for (int i=0; i<m; i++)
    {
        int x,y;
        fin>>x>>y;
        nod* nou=new nod;
        nou->y=y;
        nou->next=a[x];
        a[x]=nou;
        nou=new nod;
        nou->y=x;
        nou->next=trans[y];
        trans[y]=nou;
    }
    for (int i=1; i<=n; i++)
        if (viz1[i]==false)
            dfs1(i);
    /*for (int i=0;i<k;i++)
        cout<<steve[i]<<' ';
    cout<<endl;*/
    for (int i=k-1;i>=0;i--)
        if (viz2[steve[i]]==false)
        {
            dfs2(steve[i]);
            nr++;
        }
    fout<<nr<<'\n';
    for (int i=0;i<nr;i++)
    {
        nod* j=rez[i];
        while(j!=NULL)
        {
            fout<<j->y<<' ';
            j=j->next;
        }
        fout<<'\n';
    }
    return 0;
}