#include <bits/stdc++.h>

using u32 = unsigned;
using i64 = long long;
using u64 = unsigned long long;

constexpr int N = 1E6 + 5;

int n, m, tot = 1, head[N], to[N], next[N];

void addEdge(int u, int v) {
	to[++tot] = v;
	next[tot] = head[u];
	head[u] = tot;
}
void addEdges(int u, int v) {
	addEdge(u, v);
	addEdge(v, u);
}

int dfn[N], low[N], cnt;
bool bridge[N];

void tarjan(int x, int fr) {
	dfn[x] = low[x] = ++cnt;
	for (int i = head[x]; i; i = next[i]) {
		int y = to[i];
		if (!dfn[y]) {
			tarjan(y, i);
			low[x] = std::min(low[x], low[y]);
			if (dfn[y] == low[y]) {
				bridge[i] = bridge[i ^ 1] = 1;
			}
		} else if ((i ^ 1) != fr)
			low[x] = std::min(low[x], dfn[y]);
	}
}

int bel[N];
std::vector<int> vec[N];

void divide(int x, int id) {
	bel[x] = id;
	vec[id].push_back(x);
	for (int i = head[x]; i; i = next[i]) {
		int y = to[i];
		if (bel[y] || bridge[i]) continue;
		divide(y, id);
	}
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	std::cin >> n >> m;

	for (int i = 1; i <= m; ++i) {
		int u, v;
		std::cin >> u >> v;
		++u, ++v;
		addEdges(u, v);
	}

	for (int i = 1; i <= n; ++i) {
		if (!dfn[i]) tarjan(i, 0);
	}

	cnt = 0;
	for (int i = 1; i <= n; ++i) {
		if (!bel[i]) {
			divide(i, ++cnt);
		}
	}

	std::cout << cnt << "\n";
	for (int i = 1; i <= cnt; ++i) {
		std::cout << vec[i].size() << " ";
		for (auto x : vec[i]) {
			std::cout << x - 1 << " \n"[x == vec[i].back()];
		}
	}

	return 0;
}