#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
int n,m;
int x,y;
vector<vector<int>> A;
vector<bool> fr,frs;
vector<int> indicativ,low_link;
stack<int> S;
int k;
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(indicativ[nod]==low_link[nod])
    {
        ans.resize(ans.size()+1);
        int l=ans.size()-1;
        while(S.top()!=nod)
            {
                ans[l].push_back(S.top());
                frs[S.top()]=0;
                S.pop();
            }
        ans[l].push_back(nod);
        frs[nod]=0;
        S.pop();
    }
}
int main()
{
    cin>>n>>m;
    A.resize(n+1);
    indicativ.resize(n+1);
    low_link.resize(n+1);
    frs.resize(n+1);
    fr.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++)
    {
        sort(ans[i].begin(),ans[i].end());
        for(int j=0;j<ans[i].size();j++)
          cout<<ans[i][j]<<" ";
        cout<<'\n';
    }
    return 0;
}