#include <fstream>
#include <vector>
#include <queue>
#define N 100005
using namespace std;

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

int n, m;
vector<vector<int> > graf(N), grafInv(N), rez;
vector<int> sortare;
queue<int> coada;
bool vizitat[N];

void sortareTopologica(){
    int nod = coada.front();
    coada.pop();
    vizitat[nod] = 1;

    for(unsigned int i = 0; i < graf[nod].size(); ++i)
    if(!vizitat[graf[nod][i]]){
        coada.push(graf[nod][i]);
        sortareTopologica();
    }

    sortare.push_back(nod);
}

void kosaraju(){
    int nod = coada.front();
    coada.pop();
    vizitat[nod] = 0;

    rez[rez.size() - 1].push_back(nod);

    for(unsigned int i = 0; i < grafInv[nod].size(); ++i)
        if(vizitat[grafInv[nod][i]]){
            coada.push(grafInv[nod][i]);
            kosaraju();
        }
}

int main()
{
    in>>n>>m;

    for(int i = 1; i <= m; ++i){
        int x, y;
        in>>x>>y;

        graf[x].push_back(y);
        grafInv[y].push_back(x);
    }

    for(int i = 1; i <= n; ++i)
        if(!vizitat[i]){
            coada.push(i);
            sortareTopologica();
        }

    while(!coada.empty())coada.pop();

    vector<int> aux;
    for(int i = n - 1; i >= 0; --i)
        if(vizitat[sortare[i]]){
            rez.push_back(aux);
            coada.push(sortare[i]);
            kosaraju();
        }
    out<<rez.size()<<'\n';
    for(unsigned int i = 0; i < rez.size(); ++i){
        for(unsigned int j = 0; j < rez[i].size(); ++j)
            out<<rez[i][j]<<" ";
        out<<'\n';
    }

    in.close();
    out.close();
    return 0;
}