#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

#define lim 100010
int n,m,nr,dr;
int minm[lim], id[lim], viz[lim], st[lim];
vector <int> G[lim];
vector <vector <int>> sol;

void tarjan (int nod)
{
    viz[nod]=1;
    id[nod]=minm[nod]=++nr;
    st[++dr]=nod;
    for (auto it:G[nod])
    {
        if (!id[it])    tarjan (it);
        if (viz[it])    minm[nod] = min (minm[nod], minm[it]);
    }
    if (minm[nod]==id[nod])
    {
        vector <int> aux;
        while (nod != st[dr])
        {
            viz[st[dr]]=0;
            aux.push_back(st[dr]);
            dr--;
        }
        aux.push_back(st[dr]);
        viz[st[dr]]=0;
        dr--;
        sol.push_back(aux);
    }
}

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

    for (int i=1; i<=n; i++)
        if (!id[i]) tarjan (i);

    fout<<sol.size()<<'\n';
    for (auto it:sol)
    {
        for (auto itt:it)
            fout<<itt<<' ';
        fout<<'\n';
    }

    return 0;
}