#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

vector <int> a[100001], ta[100001], ctc[100001];

int n,m,s1[100001],s2[100001],nrc;

void citire()
{
    int i,j,k;
    f>>n>>m;
    for(k=0;k<m;k++)
    {
        f>>i>>j;
        a[i].push_back(j);
        ta[j].push_back(i);
    }

}

void dfs1(int x)
{
    int i;
    s1[x]=nrc;
    for(i=0;i<a[x].size();i++)
    {
        if(s1[a[x][i]]==0)
            dfs1(a[x][i]);
    }
}

void dfs2(int x)
{
    int i;
    s2[x]=nrc;
    for(i=0;i<ta[x].size();i++)
    {
        if(s2[ta[x][i]]==0)
            dfs2(ta[x][i]);
    }
}


int main()
{
    int i,j;
    citire();
    for(i=1;i<=n;i++)
    {
        if(s1[i]==0)
        {
            nrc++;
            dfs1(i);
            dfs2(i);
            for(j=1;j<=n;j++)
                if(s1[j]==nrc && s2[j]==nrc)
                    ctc[nrc].push_back(j);
                else
                {
                    s1[j]=0;
                    s2[j]=0;
                }
        }
    }
    cout<<nrc<<endl;
    for(i=1;i<=nrc;i++)
    {
        for(j=0;j<ctc[i].size();j++)
        {
            cout<<ctc[i][j]<<" ";
        }
        cout<<endl;
    }
    return 0;
}
/*#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int> L[50001], M[50001], CTC[50001];
int S1[50001];
int n, m;
void Citire()
{ int i, x, y;
    f>>n>>m;
for(i=1;i<=m;i++)
    { f>>x>>y;
        L[x].push_back(y);
        M[y].push_back(x);
    }
}
void DFS(int k)
{ S1[k]=1;
  int j;
    for(j=0;j<L[k].size();j++)
        if(S1[L[k][j]]==0)
          DFS(L[k][j]);
}
void DFS2(int k)
{ S1[k]=2;
int j;
    for(j=0;j<M[k].size();j++)
        if(S1[M[k][j]]==1)
          DFS2(M[k][j]);
}
void Afisare(int nr)
{int i, j;
g<<nr<<endl;
    for(i=1;i<=nr;i++)
        {for(j=0;j<CTC[i].size();j++)
            g<<CTC[i][j]<<" ";
         g<<'\n';}
}
int main()
{int i,nrc=0,j;
Citire();

    for(i=1;i<=n;i++)
        if(S1[i]==0)
        { nrc++;
          DFS(i);
          DFS2(i);
          for(j=1;j<=n;j++)
             {if(S1[j]==2)
                {CTC[nrc].push_back(j); S1[j]=-1;}
            if(S1[j]==1)
                S1[j]=0;}

        }
Afisare(nrc);
f.close();
g.close();
    return 0;
}*/