#include <fstream>
#include <vector>
#include <deque>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m,i,x,y,viz[100005],low[100005],nr,niv;
bool s[100005];
vector <int> g[100005];
vector <int> sol[100005];
deque <int> st;

void dfs(int nod){
    niv++;
    viz[nod]=low[nod]=niv;
    s[nod]=1;
    st.push_back(nod);
    for(int i=0;i<g[nod].size();i++){
        int nou=g[nod][i];
        if(!viz[nou]){
            dfs(nou);
            low[nod]=min(low[nod],low[nou]);
        }
        else if(s[nou])
            low[nod]=min(low[nod],viz[nou]);
    }
    if(viz[nod]==low[nod]){ ///nodul e radacina
        nr++;
        int x=st.back();
        st.pop_back();
        while(x!=nod){
            s[x]=0;
            sol[nr].push_back(x);
            x=st.back();
            st.pop_back();
        }
        s[x]=0;
        sol[nr].push_back(x);
    }
}

int main()
{
   fin>>n>>m;
   for(i=1;i<=m;i++){
        fin>>x>>y;
        g[x].push_back(y);
   }
   for(i=1;i<=n;i++)
      if(!viz[i])
          dfs(i);
    fout<<nr<<'\n';
    for(i=1;i<=nr;i++){
        for(int j=0;j<sol[i].size();j++)
            fout<<sol[i][j]<<' ';
        fout<<'\n';
    }
    return 0;
}