#include<bits/stdc++.h>

typedef long long ll;
typedef std::pair<ll, ll> P;

constexpr ll INF = 1e15;
constexpr ll mod = 998244353;

#define rep(i,n) for(int i = 0; i < int(n); i++)
using namespace std;

template<class T> inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }

namespace atcoder {

    template <class E> struct csr {
        std::vector<int> start;
        std::vector<E> elist;
        csr(int n, const std::vector<std::pair<int, E>>& edges)
            : start(n + 1), elist(edges.size()) {
            for (auto e : edges) {
                start[e.first + 1]++;
            }
            for (int i = 1; i <= n; i++) {
                start[i] += start[i - 1];
            }
            auto counter = start;
            for (auto e : edges) {
                elist[counter[e.first]++] = e.second;
            }
        }
    };

    // Reference:
    // R. Tarjan,
    // Depth-First Search and Linear Graph Algorithms
    struct scc_graph {
    public:
        scc_graph(int n) : _n(n) {}

        int num_vertices() { return _n; }

        void add_edge(int from, int to) { edges.push_back({ from, {to} }); }

        // @return pair of (# of scc, scc id)
        std::pair<int, std::vector<int>> scc_ids() {
            auto g = csr<edge>(_n, edges);
            int now_ord = 0, group_num = 0;
            std::vector<int> visited, low(_n), ord(_n, -1), ids(_n);
            visited.reserve(_n);
            auto dfs = [&](auto self, int v) -> void {
                low[v] = ord[v] = now_ord++;
                visited.push_back(v);
                for (int i = g.start[v]; i < g.start[v + 1]; i++) {
                    auto to = g.elist[i].to;
                    if (ord[to] == -1) {
                        self(self, to);
                        low[v] = std::min(low[v], low[to]);
                    }
                    else {
                        low[v] = std::min(low[v], ord[to]);
                    }
                }
                if (low[v] == ord[v]) {
                    while (true) {
                        int u = visited.back();
                        visited.pop_back();
                        ord[u] = _n;
                        ids[u] = group_num;
                        if (u == v) break;
                    }
                    group_num++;
                }
            };
            for (int i = 0; i < _n; i++) {
                if (ord[i] == -1) dfs(dfs, i);
            }
            for (auto& x : ids) {
                x = group_num - 1 - x;
            }
            return { group_num, ids };
        }

        std::vector<std::vector<int>> scc() {
            auto ids = scc_ids();
            int group_num = ids.first;
            std::vector<int> counts(group_num);
            for (auto x : ids.second) counts[x]++;
            std::vector<std::vector<int>> groups(ids.first);
            for (int i = 0; i < group_num; i++) {
                groups[i].reserve(counts[i]);
            }
            for (int i = 0; i < _n; i++) {
                groups[ids.second[i]].push_back(i);
            }
            return groups;
        }

    private:
        int _n;
        struct edge {
            int to;
        };
        std::vector<std::pair<int, edge>> edges;
    };

}  // namespace atcoder


int main() {
    ll n, m;
    cin >> n >> m;
    atcoder::scc_graph g(n);
    rep(i, m) {
        int a, b;
        cin >> a >> b;
        g.add_edge(a, b);
    }
    auto p = g.scc();
    cout << p.size() << endl;
    for (auto id : p) {
        cout << id.size() << " ";
        for (auto v : id) {
            cout << v << " ";
        }
        cout << endl;
    }
    return 0;
}


Measured memory_bytes: 40596