#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

#define NMAX 100003

using namespace std;

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

vector <int> G[NMAX] , GT[NMAX] , CTC[NMAX];
stack <int> stiva;
bool viz[NMAX];
int nr_CTC = 0;

void dfs1(int nod){
    viz[nod] =1;
    int size_ = G[nod].size();
    for(int i=0;i<size_;i++){
        if(!viz[ G[nod][i] ])
            dfs1(G[nod][i]);
    }
    stiva.push(nod);
}

void dfs2(int nod){
    viz[nod] =0;
    CTC[nr_CTC].push_back(nod);
    int size_ = GT[nod].size();
    for(int i =0 ; i<size_ ; i++){
        if(viz[ GT[nod][i] ])
            dfs2( GT[nod][i] );
    }
}

int main()
{
    int x, y , n , i , m;
    fin>>n>>m;
    while(m--){
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    dfs1(1);
    while(!stiva.empty())
    {
        x = stiva.top();
        if(viz[x] == 1){
            nr_CTC ++ ;
            dfs2(x);
        }
        stiva.pop();
    }
    fout<<nr_CTC<<'\n';
    for(int i = 1; i<=nr_CTC ; i++){
        sort(CTC[i].begin() , CTC[i].end());
        for(int j = 0 ; j<CTC[i].size() ; j++)
            fout<<CTC[i][j]<<' ';
        fout<<'\n';
    }
    return 0;
}