#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],nrsol=0,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])

    {

      ++nrsol;

      comp.emplace_back();

      comp.back().emplace_back(u);

      disc[u]=low[u]=inf;

      while(sol.back()!=u)

      {

          comp.back().emplace_back(sol.back());

          disc[sol.back()]=low[sol.back()]=inf;

          sol.pop_back();

      }

      sol.pop_back();

    }

}

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<<nrsol<<"\n";
    for(auto &i:comp)
    {
        for(int j:i)
            fout<<j<<" ";
        fout<<"\n";
    }
    return 0;
}