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

using namespace std;

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

#define lim 100010
vector <int> G[lim], Gt[lim], ans;
vector <vector <int> > rez;
int viz[lim], st[lim], dr;

void dfs (int nod)
{
    viz[nod]=1;
    for (auto it:G[nod])
        if (!viz[it])
            dfs(it);
    st[++dr]=nod;
}

void dfs2 (int nod)
{
    viz[nod]=1;
    ans.push_back(nod);
    for (auto it:Gt[nod])
        if (!viz[it])
            dfs2(it);
}

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

    for (int i=1; i<=n; i++)
        if (!viz[i])
            dfs (i);
    memset (viz, 0, sizeof(viz));
    for (int i=n; i>=1; i--)
        if (!viz[st[i]])
        {
            ans.clear();
            dfs2(st[i]);
            rez.push_back(ans);
        }

    fout<<rez.size()<<'\n';
    for (unsigned i=0; i<rez.size(); i++, fout<<'\n')
        for (auto it:rez[i])
            fout<<it<<' ';

    return 0;
}