#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, cnt=0;

vector<vector<int>> adj, inv, comp;
vector <int> viz,ord;

void DFS(int nod){
    viz[nod] = 1;
    for(int i : adj[nod]){
        if(viz[i]==0) DFS(i);
    }
    ord.push_back(nod);
}
void DFSinv(int nod){
    viz[nod] = 1;
    comp[cnt].push_back(nod);
    for(int i :inv[nod]){
        if(viz[i]==0) DFSinv(i);
    }
}


int main()
{
    fin>>n>>m;
    adj.resize(n+5);
    viz.resize(n+5,0);
    inv.resize(n+5);
    comp.resize(n+5);


    for(int i = 1; i<=m; i++){
        int x,y;
        fin>>x>>y;
        adj[x].push_back(y);
        inv[y].push_back(x);
    }

    for(int i=1; i<=n; i++){
        if(viz[i] ==0){
            DFS(i);
        }
    }
    for(int i=1; i<=n; i++)
        viz[i]=0;

    for(int i=ord.size()-1; i>=0; i--){
        int nod=ord[i];
        if(viz[nod]==0){
            DFSinv(nod);
            cnt++;
        }
    }
    fout<<cnt<<endl;

    for(int i=0; i<cnt; i++){
        for(int nod : comp[i])
            fout<<nod<<" ";
        fout<<endl;
    }
    return 0;
}