#include<algorithm>
#include<iomanip> 
#include<iostream>
#include<sstream>
#include<cstring>
#include<cstdlib>
#include<climits>
#include<fstream>
#include<cctype>
#include<cstdio>
#include<string>
#include<vector>
#include<queue>
#include<stack>
#include<cmath>
#include<map>
#include<set>
using namespace std;

#define pb push_back
#define mp make_pair
#define Y second
#define X first

#define fi freopen("input.txt","r",stdin)
#define fo freopen("output.txt","w",stdout)

const double pi     =   acos(-1.0);
const double eps    =   1e-8;

/*Solution code starts here */

/*
ios_base::sync_with_stdio(false);

*/
                
                    
#define MAX_V 100000
 
vector<int> L[MAX_V],C[MAX_V];

int V,dfsPos,dfsNum[MAX_V],lowlink[MAX_V],num_scc;

bool in_stack[MAX_V];

stack<int> S;
 
void tarjan(int v){
    dfsNum[v] = lowlink[v] = dfsPos++;
    S.push(v); in_stack[v] = true;
    
    for(int i = L[v].size()-1;i>=0;--i){
        int w = L[v][i];
        if(dfsNum[w]==-1){
            tarjan(w);
            lowlink[v] = min(lowlink[v],lowlink[w]);
        }else if(in_stack[w]) lowlink[v] = min(lowlink[v], lowlink[w]);
    }
    
    if(dfsNum[v]==lowlink[v]){
        vector<int> com;
        int aux;
        
        do{
            aux = S.top(); S.pop();
            com.push_back(aux);
            in_stack[aux] = false;
        }while(aux!=v);
        
        C[num_scc] = com;
        ++num_scc;
    }
}
 
void build_scc(){
    memset(dfsNum,-1,sizeof(dfsNum));
    memset(in_stack,false,sizeof(in_stack));
    dfsPos = num_scc = 0;
    
    for(int i = 0;i<V;++i)
        if(dfsNum[i]==-1)
            tarjan(i);
}


int main()
{
int ed,a,b;

ios_base::sync_with_stdio(false);

freopen("ctc.in","r",stdin);
freopen("ctc.out","w",stdout);

 cin>>V>>ed;

  for(int i=1;i<=ed;i++)
   { cin>>a>>b;

     a--;b--;
  
    L[a].pb(b);
   }

 build_scc();

 cout<<num_scc<<"\n";;

 for(int i=0;i<num_scc;i++)
 {

    for(int j=0;j<C[i].size();j++)
      cout<<C[i][j]+1<<" ";

     cout<<endl;
  }




  

     


return 0;
}