#include<fstream>
#include<vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector<int>graph[100005],grapht[100005],fin[100005];
bool viz[100005];
int poz[100005];
int n,m,x,y,con,k;
void dfs(int nod)//dfs grafului normal
{
    viz[nod]=1;
    for(int i=0;i<graph[nod].size();i++)
      if(viz[graph[nod][i]]==0)
        dfs(graph[nod][i]);
    k++;
    poz[k]=nod;//vector de post ordine pentru a putea afla componentele tare conexe apeland dfst in functie de postordinea formata
}
void dfst(int nod)//dfs pentru graful transpus+construirea solutiei
{
    viz[nod]=0;
    fin[con].push_back(nod);
    for(int i=0;i<grapht[nod].size();i++)
      if(viz[grapht[nod][i]]==1)
        dfst(grapht[nod][i]);
}
int main()
{
    f>>n>>m;
    for(int i=1;i<=m;i++)
    {
        f>>x>>y;
        graph[x].push_back(y);//construiesc graful orientata
        grapht[y].push_back(x);//construiesc graful orientat transpus
    }
    for(int i=1;i<=n;i++)
      if(viz[i]==0)
        dfs(i);
    for(int i=n;i>=1;i--)
      if(viz[poz[i]]==1)
      {
          con++;
          dfst(poz[i]);
      }
    g<<con<<"\n";
    for(int i=1;i<=con;i++)
    {
        for(int j=0;j<fin[i].size();j++)
          g<<fin[i][j]<<" ";
        g<<"\n";
    }
    return 0;
}