#include <bits/stdc++.h>
#define NMAX 100010
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector<int> G[NMAX],GT[NMAX],comp[NMAX];
int n,m;
int nrcomp,nr;
int ordine[NMAX];
bitset <NMAX> viz;
void DFS(int x){
    viz[x]=true;
    for(int i=0;i<G[x].size();i++)
        if(!viz[G[x][i]])DFS(G[x][i]);
    ordine[++nr] = x;
}
void citire(){
    f>>n>>m;
    for(int i=1,x,y;i<=m;i++){
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void DFST(int x){
    comp[nrcomp].push_back(x);
    viz[x]=0;
    for(int i=0; i<GT[x].size();i++){
        if(viz[GT[x][i]])DFST(GT[x][i]);
    }
}
void afisare(){
    g<<nrcomp<<"\n";
    for(int i=1;i<=nrcomp;i++){
        for(int j=0;j<comp[i].size();j++){
            g<<comp[i][j]<<" ";
        }
        g<<"\n";
    }
}
int main()
{
    citire();
    for(int i=1;i<=n;i++)
        if(!viz[i])DFS(i);
    for(int i=n;i>0;i--)
        if(viz[ordine[i]]){
            nrcomp++;
            DFST(ordine[i]);
        }
   afisare();
    return 0;
}