#include <fstream>

#include <vector>

#define nmax 100000

#define mmax 200000

#define inf 0x3f3f3f3f

using namespace std;

ifstream fin("ctc.in");

ofstream fout("ctc.out");

int n,m,disc[nmax+5],low[nmax+5],indice=0;

vector<int> v[nmax+5],sol;

vector < vector<int> > comp;

bool viz[nmax+5];

int minv(int x, int y)

{

    return x<y?x:y;

}

void dfs(int u, int parent)

{
    disc[u]=low[u]=++indice;
    viz[u]=1;
    sol.emplace_back(u);
    for(int i : v[u])
        if(!viz[i])
        {
            dfs(i,u);
            low[u]=minv(low[u],low[i]);
        }
        else
            low[u]=minv(low[u],low[i]);
    if(disc[u]==low[u])
    {
      comp.emplace_back();
      do
      {
          comp.back().emplace_back(sol.back());
          sol.pop_back();
      }while(*(&(sol.back())+1)!=u);
    }

}

int main()

{

    fin>>n>>m;

    int x,y;
    for(int i=1;i<=m;i++)
        fin>>x>>y,v[x].emplace_back(y);
    for(int i=1;i<=n;i++)
        if(!viz[i])
        dfs(i,0);
    fout<<comp.size()<<"\n";
    for(auto &i:comp)
    {
        for(int j:i)
            fout<<j<<" ";
        fout<<"\n";
    }
    return 0;
}