#include <cstdio>
#include <stack>
#include <vector>
#include <bitset>
#define Nmax 100001
using namespace std;
vector <int> g[Nmax];
vector <int> g_inv[Nmax];
vector <int> solutie[Nmax];
stack <int> coada;
bitset <Nmax> viz;
int n,nr,m;

void read()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d %d",&n,&m);
    int x,y;
    for(int i = 0 ; i < m ; i++)
    {
        scanf("%d %d",&x,&y);
        g[x].push_back(y);
        g_inv[y].push_back(x);
    }
}

void parcurgere(int start)
{
    viz[start] = true;
    vector <int> :: iterator it;
    for(it = g[start].begin(); it != g[start].end() ; it++)
    {
        if(!viz[*it])
            parcurgere(*it);
    }
    coada.push(start);
}

void afisare(int x)
{
  for(int i = 0 ; i < x ; i++)
  {
      for(vector <int> :: iterator it = solutie[i].begin(); it != solutie[i].end() ; it++)
            printf("%d ",*it);
     printf("\n");
  }
}


void parcurgere_inv(int start,int nr)
{
    solutie[nr].push_back(start);
    viz[start] = true;
    for(vector <int> :: iterator it = g_inv[start].begin(); it != g_inv[start].end() ; it++)
    {
        if(!viz[*it])
            parcurgere_inv(*it,nr);
    }
}

void rezolvare()
{
    nr = 0;
    for(int i = 1 ; i <= n ; i++)
    {
        if(!viz[i])
            parcurgere(i);
    }
    viz = false ;
    while(!coada.empty())
    {
        int x = coada.top();
        coada.pop();
        if(!viz[x])
        {
            parcurgere_inv(x,nr);
            nr++;
        }
    }
    printf("%d\n",nr);
    afisare(nr);
}



int main()
{
    read();
    rezolvare();
    return 0;
}