#include <iostream>
#include <fstream>
#include <stack>
#include<fstream>
#include<vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
stack<int>stiva;
bool viz[100001];
vector<int> lista[100001], listatr[100001],ctc[100001];
int n,m,i,nr_ctc,a,b,j,nod;

void dfs(int nod)
{
    viz[nod] = true;
    for(auto inod : lista[nod])
        if(viz[inod] == false)
            dfs(inod);
    stiva.push(nod);
}

void dfs_tr(int nod)
{
    viz[nod]=false;
    ctc[nr_ctc].push_back(nod);
    for (auto inod : listatr[nod])
        if (viz[inod] == true)
            dfs_tr(inod);
}
int main()
{
    f>>n>>m;
    for(i=0; i<m; i++)
    {
        f>>a>>b;
        lista[a].push_back(b);
        listatr[b].push_back(a);
    }
     for(i=1; i<=n; i++)
        if(viz[i] == false)
            dfs(i);

    while(!stiva.empty()){
        nod=stiva.top();
        stiva.pop();
        if(viz[nod]==true){
            nr_ctc++;
            dfs_tr(nod);
        }

    }
    g<<nr_ctc<<endl;
    for(i = 1; i<=nr_ctc; i++){
        for(j = 0; j < ctc[i].size(); j++)
            g<<ctc[i][j]<<" ";
        g<<endl;
    }
    return 0;
}