#include <fstream>
#include <vector>
#include <set>

using namespace std;

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

const int Nmax = 1e6 + 5;
int cnt = 0;
vector<int> g[Nmax], gt[Nmax];
vector<int> topo, use;
set<int> group[Nmax];

void dfs(int nod) {
    use[nod] = 1;
    for (int i : g[nod])
        if (!use[i])
            dfs(i);

    topo.push_back(nod);
}

void dfst (int nod, int idx) {
    use[nod] = 1;
    for (int i : gt[nod])
        if (!use[i])
            dfst(i, idx);

    group[idx].insert(nod);
}

int main()
{
    int n,m;
    cin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x,y;
        cin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }

    //topo = {group a, group b, ... group x}
    use = vector<int>(n + 1, 0);
    for (int i = 1; i <= n; i++)
        if (!use[i])
            dfs(i);

    //pentru fiecare nod in ordinea topo, ii inchidem groupa de ctc
    use = vector<int>(n + 1, 0);
    for (auto it = topo.rbegin(); it != topo.rend(); ++it) {
        if (!use[*it]) {
            dfst(*it, cnt);
            cnt++;
        }
    }

    if (cnt == 0)
        cout << 1 << endl;
    else
        cout << cnt << endl;
    for (int i = 0; i < cnt; i++, cout << endl)
        for (int j : group[i])
            cout << j << " ";

    return 0;
}