#include<iostream>
#include<fstream>
#include<cmath>
#include<algorithm>
#include<vector>
#include<bitset>
#include<cstring>
#include<queue>
#include<stack>

#define ull unsigned long long
#define ll long long
#define pb push_back
#define FOR(a,b,c) for (int a=b;a<=c; ++a)
#define ROF(a,b,c) for (int a=b;a>=c; --a)
#define Nmax 100010

// algoritmul kosaraju

using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
int N,M,nrcomp;

vector<int> vorig[Nmax];
vector<int> vtrans[Nmax];
vector<int> componente[Nmax];
vector<int> ord;
bitset<Nmax> verif;

// vorig=listele de adiacenta pentru graful original
// vtrans=listele de adiacenta pentru graful transpus

void dfs_p(int,vector<int>*);
void dfs_m(int,vector<int>*);

int main()
{
    f>>N>>M;
    FOR (i,1,M) {
        int x,y;
        f>>x>>y;
        vorig[x].pb(y);
        vtrans[y].pb(x);
    }
    FOR (i,1,N) {
        if (!verif.test(i)) {
            dfs_p(i,vorig); // se aranjeaza nodurile descrescator in functie de timpul de iesire
        }
    }
    FOR (i,1,N) {
        verif.set(i,0);
    }
    while (ord.size()) {
        int nod=ord.back();
        ord.pop_back();
        if (!verif.test(nod)) {
            ++nrcomp;
            dfs_m(nod,vtrans); // se stabilesc componentele tare-conexe
        }
    }
    g<<nrcomp<<'\n';
    FOR (i,1,nrcomp) {
        vector<int>::iterator it;
        for (it=componente[i].begin();it<componente[i].end();++it) {
            g<<(*it)<<' ';
        }
        g<<'\n';
    }
    f.close();g.close();
    return 0;
}

void dfs_p(int nod,vector<int> *v) {
    verif.set(nod,1);
    for (unsigned int k=0;k<v[nod].size();++k) {
        if (!verif.test(v[nod][k])) {
            dfs_p(v[nod][k],v);
        }
    }
    ord.pb(nod);
}

void dfs_m(int nod,vector<int> *v) {
    verif.set(nod,1);
    componente[nrcomp].pb(nod);
    for (unsigned int k=0;k<v[nod].size();++k) {
        if (!verif.test(v[nod][k])) {
            dfs_m(v[nod][k],v);
        }
    }
}