#include <iostream>
#include <vector>
#include <fstream>
#include <deque>
#include <bitset>
#define dim 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
bitset<dim> iq;
deque<int> q;
vector <int> L[dim],aux;
vector< vector<int> > sol;
int low[dim],niv[dim],g,n,m,i,x,y;
void dfs(int nod){
iq[nod]=1;
niv[nod]=++g;
low[nod]=g;
q.push_back(nod);
for(auto it:L[nod]){
    if(iq[it]==0){
        dfs(it);
    }
    low[nod]=min(low[nod],low[it]);
}
if(low[nod]==niv[nod]){
        aux.clear();
        int x;
    while(x!=nod){
        x=q.back();
        q.pop_back();
        aux.push_back(x);
    }
    sol.push_back(aux);
}
}
int main()
{
   fin>>n>>m;
   for(i=1;i<=m;i++){
    fin>>x>>y;
    L[x].push_back(y);
   }
   for(i=1;i<=n;i++){
    if(iq[i]==0){
        dfs(i);
    }
   }
   fout<<sol.size()<<"\n";
   for(auto &vec:sol){
        for(auto &it:vec)
            fout<<it<<" ";
        fout<<"\n";
   }
}