#include<iostream>
#include<vector>
#include<fstream>
#include<stack>

#define MAX 100000

using namespace std;

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

vector <int> graf1[MAX],graf2[MAX],comp_conexe[MAX];
stack <int> s;
int nr_comp_conexe,viz[MAX];

void dfs1(int nod ){

    vector <int > ::iterator it;

    viz[nod]=1;

    for( it = graf1[nod].begin() ; it < graf1[nod].end(); it++ )
        if(viz[*it]==0)
            dfs1(*it);

    s.push(nod);

}

void dfs2(int nod){

    vector <int > ::iterator it;

    viz[nod]=0;
    comp_conexe[nr_comp_conexe].push_back(nod);

    for( it = graf2[nod].begin() ; it < graf2[nod].end(); it++ )
        if(viz[*it]==1)
            dfs2(*it);

}

void tarjan( ){

    int val;

    while(!s.empty()){


        if(viz[s.top()]==1){
            dfs2(s.top());
            nr_comp_conexe++;
        }

        s.pop();

    }

}

void afisare(){

    vector <int > ::iterator it;
    unsigned int i;
    int j;

    out<<nr_comp_conexe<<endl;

    for( j = 0 ; j < nr_comp_conexe ; j++ ){
        for( it = comp_conexe[j].begin() ; it < comp_conexe[j].end(); it++)
            out<<*it<<" ";
        out<<endl;
    }
}


int main(){

    int n,m,x,y,i;

    in>>n>>m;

    for( i = 1; i <= m; i++){

        in>>x>>y;
        graf1[x].push_back(y);
        graf2[y].push_back(x);

    }

    for(i = 1 ; i <= n ; i++ )
        if(viz[i]==0)
            dfs1(i);


    tarjan();

    afisare();

    return 0;
}