#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define MAX 100010

typedef vector <int> :: iterator iter;
vector <int> G[MAX], Gt[MAX], ans;
vector <vector <int> > rez;
int viz[MAX], st[MAX], dr;

void df(int nod)
{
    viz[nod] = 1;
    for(iter it = G[nod].begin() ; it != G[nod].end() ; it++)
    {
        if(!viz[*it])
            df(*it);
    }
    st[++dr] = nod;
}

void df2(int nod)
{
    viz[nod] = 1;
    ans.push_back(nod);
    for(iter it = Gt[nod].begin() ; it != Gt[nod].end() ; it++)
    {
        if(!viz[*it])
            df2(*it);
    }
}

int main()
{
    int n, m, i, x, y;
    fin >> n >> m;
    for(i = 1 ; i <= m ; i++)
    {
        fin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for(i = 1 ; i <= n ; i++)
    {
        if(!viz[i])
            df(i);
    }
    memset(viz, 0, sizeof(viz));
    for(i = n ; i >= 1 ; i--)
    {
        if(!viz[st[i]])
        {
            //cout << st[i] ;
            ans.clear();
            df2(st[i]);
            rez.push_back(ans);
        }
    }
    fout << rez.size() << "\n";
    for(i = 0 ; i < rez.size() ; i++)
    {
        for(iter it = rez[i].begin() ; it != rez[i].end() ; it++)
        {
            fout << *it << " ";
        }
        fout << "\n";
    }

}