#include <iostream>
#include <fstream>
#include <queue>
#include <vector>

#define VALMAX 100005

using namespace std;

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


vector<int> componente[VALMAX+1];

struct nod{

nod *next;
int val;

};

class OrientedGraph{

protected:
    nod *varfuri[VALMAX];
    nod *varfuriT[VALMAX];
    int nrVarfuri;
    int nrMuchii;
    int varfStart;
    int vizitat[VALMAX + 1];
    int vizitatT[VALMAX + 1];
    int drc[VALMAX + 1];

public:
    OrientedGraph(){
        vizitAll();
        makeDrc0();
    }

    OrientedGraph(int nrV, int nrM): nrVarfuri(nrV), nrMuchii(nrM){
        vizitAll();
        makeDrc0();
    }

void vizitAll(){
    for(int i = 1;i<=VALMAX;++i){
        vizitat[i] = 0;
        vizitatT[i] = 0;
    }
}

void makeDrc0(){
    for(int i = 1;i<=VALMAX;++i){
        drc[i] = 0;
    }
}

void citireOrientat(){
    if(!nrVarfuri)fin>>nrVarfuri>>nrMuchii; /// default behavior
    for(int i = 1;i<=nrMuchii;++i){
        int x, y;
        fin>>x>>y;
        nod *p = new nod;
        p->val = y;
        p->next = varfuri[x];
        varfuri[x] = p;

        p = new nod;
        p->val = x;
        p->next = varfuriT[y];
        varfuriT[y] = p;

    }
}

void afisare(){

    for(int i = 1;i<=nrVarfuri;++i){
        nod *p = varfuri[i];
        cout<<"varf: "<<i<<"...: ";
        while(p){
            cout<<p->val<<" ";
            p = p->next;
        }
        cout<<endl;
    }

}


};

class ComponenteTareConexe: public OrientedGraph{

public:
    ComponenteTareConexe(): OrientedGraph(){}
    ComponenteTareConexe(int nrV, int nrM): OrientedGraph(nrV, nrM){}


void dfs1(int varf){

vizitat[varf] = 1;
nod *p = varfuri[varf];
while(p){
    if(!vizitat[p->val]){
        dfs1(p->val);
    }
    p = p->next;
}

}

void dfs2(int varf){

vizitatT[varf] = 1;
nod *p = varfuriT[varf];
while(p){
    if(!vizitatT[p->val]){
        dfs2(p->val);
    }
    p = p->next;
}

}


void componenteTare(){

    int contorComp = 0;

    for(int i = 1;i<=nrVarfuri;++i){
        if(drc[i] == 0){
            contorComp++;
            vizitAll();
            dfs1(i);
            dfs2(i);
            for(int i = 1;i<=nrVarfuri;++i){
                if(vizitat[i] && vizitatT[i]){
                    componente[contorComp].push_back(i);
                }
            }
        }
    }
    fout<<contorComp<<endl;
    for(int i = 1;i<=contorComp;++i){
        int lungime = componente[i].size();
        for(int j = 0;j<lungime;++j){
            cout<<'d';
            fout<<componente[i][j]<<" ";
        }
        fout<<endl;
    }


}

};


int main()
{

    ComponenteTareConexe g;
    g.citireOrientat();
    //g.afisare();
    g.componenteTare();

    return 0;
}