#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
unsigned int n,m, nr;
bool a[100001][100001], viz[100001];
vector <int> x[100001];

void citire()
{
    int i,j,k;
    f>>n>>m;
    for(k=1; k<=m; k++)
    {
        f>>i>>j;
        a[i][j]=1;
    }
}

void parcurgere()
{
    int i,j,k;
    for(i=1; i<=n; i++)
        a[i][i]=1;
    for(k=1; k<=n; k++)
    for(i=1; i<=n; i++)
    for(j=1; j<=n; j++)
      if(a[i][j]==0)
      {
        a[i][j]=a[k][j]*a[i][k];
      }
}

void componente()
{
    int i,j;
    for(i=1; i<=n; i++)
        if(viz[i]==0)
        {nr++;
         for(j=1; j<=n; j++)
            if(a[i][j]==1 && a[j][i]==1)
            {x[nr].push_back(j); viz[j]=1;}
        }
}

int main()
{
    citire();
    parcurgere();
    componente();
    int i,j;
    g<<nr<<endl;
    for(i=1; i<=n; i++)
        {for(j=0; j<x[i].size(); j++)
        g<<x[i][j]<<" ";
    g<<endl;}
    f.close();
    g.close();
    return 0;
}