#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
int n,m;
int k;
vector<vector<int>> A;
vector<int> low_link,indicativ;
vector<bool> fr,frs;
stack<int> S;
int x,y;
vector<vector<int>> ans;
void dfs(int nod)
{
    indicativ[nod]=k++;
    low_link[nod]=indicativ[nod];
    S.push(nod);
    frs[nod]=1;

    for(int i=0;i<A[nod].size();i++)
    {
        int vecin=A[nod][i];
        if(!fr[vecin])
        {
            fr[vecin]=1;
            dfs(vecin);
        }
        if(frs[vecin])
           low_link[nod]=min(low_link[nod],low_link[vecin]);
    }
    if(low_link[nod]==indicativ[nod])
    {
        ans.resize(ans.size()+1);
        while(S.top()!=nod)
        {
            ans[ans.size()-1].push_back(S.top());
            frs[S.top()]=0;
            S.pop();
        }
        ans[ans.size()-1].push_back(S.top());
        S.pop();
        frs[nod]=0;
    }
}
int main()
{
    cin>>n>>m;
    A.resize(n+1);
    low_link.resize(n+1);
    indicativ.resize(n+1);
    fr.resize(n+1);
    frs.resize(n+1);
    for(int i=0;i<m;i++)
    {
        cin>>x>>y;
        A[x].push_back(y);
    }
    for(int i=1;i<=n;i++)
      if(!fr[i])
      {
          fr[i]=1;
          dfs(i);
      }
    cout<<ans.size()<<'\n';
    for(int i=0;i<ans.size();i++)
    {
        for(int j=0;j<ans[i].size();j++)
           cout<<ans[i][j]<<" ";
        cout<<'\n';
    }
    return 0;
}