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

using namespace std;

/// cu plus-minus
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

#define lim 100010
int n,m,st[lim],dr;
vector <int> G[lim],Gt[lim];
vector <vector <int>> sol;
bool viz[lim];

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

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

int main()
{
    int 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);
    for (int i=1; i<=n; i++)    viz[i]=0;
    dr=0;
    for (int i=n; i>=1; i--)
        if (!viz[st[i]])
        {
            sol.resize(++dr);
            dfs_t(st[i]);
        }

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

    fout.close();
    return 0;
}