#include <bits/stdc++.h>

using namespace std;
vector <int> graf[100001];
vector <int> graf_inversat[100001];
bool viz[100001];
vector <int> v;
vector <int> componente[100001];
int cate_componente;
void dfs1 (int nod)
{
    viz[nod] = 1;
    for (auto x:graf[nod])
        if (viz[x]==0)
            dfs1(x);
    v.push_back(nod);
}
void dfs2 (int nod)
{
    componente[cate_componente].push_back(nod);
    viz[nod] = 0;
    for (auto x:graf_inversat[nod])
        if (viz[x])
            dfs2(x);
}
int main()
{
    ifstream fin ("ctc.in");
    ofstream fout ("ctc.out");
    int n, m;
    fin >> n >> m;
    for (int i = 1; i<=m; ++i)
    {
        int x, y;
        fin >> x >> y;
        graf[x].push_back(y);
        graf_inversat[y].push_back(x);
    }
    for (int i = 1; i<=n; ++i)
        if (viz[i] == 0)
            dfs1(i);
    for (int i = n-1; i>=0; --i)
        if (viz[v[i]])
        {
            cate_componente++;
            dfs2(v[i]);
        }
    fout << cate_componente << '\n';
    for (int i = 1; i<=cate_componente; ++i)
    {
        sort(componente[i].begin(), componente[i].end());
        for (auto x:componente[i])
            fout << x << " ";
        fout << '\n';
    }
    return 0;
}