#include <iostream>
#include <fstream>
#include <bitset>
#include <vector>
#include <algorithm>
#define NMAX 100002

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

int n,m;
vector <int> g[NMAX], g_n[NMAX], aux, aux2;
vector<vector<int>> rasp;
bitset <NMAX> viz;

void citire()
{
    in >> n >> m;
    int x,y;
    for(int i = 1; i <= m; ++i)
    {
        in >> x >> y;
        g[x].push_back(y);
        g_n[y].push_back(x);
    }
}

void dfs1(int nod)
{
    viz[nod] = true;
    for(auto i: g[nod])
        if(not viz[i])
            dfs1(i);
    aux.push_back(nod);
}

void dfs2(int nod)
{
    viz[nod] = true;
    aux2.push_back(nod);
    for(auto i: g_n[nod])
        if(not viz[i])
            dfs2(i);
}

void afish()
{
    out << rasp.size() << '\n';
    for(auto i: rasp)
    {
        for(auto j: i)
            out << j << ' ';
        out << '\n';
    }
}

int main()
{
    citire();
    for(int i = 1; i <= n; ++i)
        if(not viz[i])
            dfs1(i);
    viz.reset();
    reverse(aux.begin(),aux.end());
    for(auto i : aux)
        {
            if(not viz[i])
            {
                aux2.clear();
                dfs2(i);
                rasp.push_back(aux2);
            }
        }
    afish();
    return 0;
}