#include <bits/stdc++.h>
#include <vector>
#define NMAX 100002
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,poz;
///graful G reprezentat prin liste de adiacenta
vector<int> G[NMAX];
///transpus
vector<int> GT[NMAX];
bool viz[NMAX];
int nr;///nr de componente tare conexe
vector<int> ctc[NMAX];
int postordine[NMAX];

void citire();
void afisare();

void dfs(int x);
void dfst(int x);
int main()
{
    citire();
    ///parcurg dfs graful g retinand varfurile in postordine
    for(int i=1;i<=n;i++)
        if(viz[i]==0)
            dfs(i);
    ///parcurg vectorul postordine de la dreapta la stanga si DFST
    for(int i=n;i>0;i--)
        if(viz[postordine[i]]==1) ///acest varf este nevizitat in GT
            {
             nr++;
             dfst(postordine[i]);
            }
    afisare();
    return 0;
}
void citire(){
    int i,x,y,m;
fin>>n>>m;
for(i=0;i<m;i++){
    fin>>x>>y;
    G[x].push_back(y);
    GT[y].push_back(x);
    }
}

void afisare(){
fout<<nr<<endl;
for(int i=1;i<=nr;i++){
    for(int j=0;j<ctc[i].size();j++)
        fout<<ctc[i][j]<<' ';
    fout<<endl;
}
}

void dfs(int x){
int i;
viz[x]=1;
for(i=0;i<G[x].size();i++)
    if(viz[G[x][i]]==0) ///adiacente
        dfs(G[x][i]);
postordine[++poz]=x;
}

void dfst(int x){
int i;
viz[x]=0; ///retin acest varf in componenta conexa curenta
ctc[nr].push_back(x);
for(i=0;i<GT[x].size();i++)
    if(viz[GT[x][i]]==1) ///adiacente
        dfst(GT[x][i]);
}