#include <bits/stdc++.h>
using namespace std;
const int MAXN = 500005;
typedef unsigned long long ull;
vector<int> G[MAXN];
int dfn[MAXN], low[MAXN], instk[MAXN], times;
int scc[MAXN], btot; stack<int> stk;
void dfs1(int u, int f) {
	dfn[u] = low[u] = ++times; instk[u] = 1; stk.push(u); for (int v : G[u]) {
		if (v == f) {f = -1; continue;}
		if (dfn[v] == 0) dfs1(v, u), low[u] = min(low[u], low[v]);
		else if (instk[v]) low[u] = min(low[u], dfn[v]);
	}
	if (dfn[u] == low[u]) {
		int y; btot++; do {
			y = stk.top(); stk.pop(); instk[y] = 0; scc[y] = btot;
		} while (y != u);
	}
}
map<ull, int> mp; map<ull, pair<int, int> > etmp; ull exor[MAXN]; int fa[MAXN];
mt19937_64 rnd(time(0));
void dfs2(int u, int f) {
	dfn[u] = 1; instk[u] = 1; fa[u] = f; for (int v : G[u]) {
		if (scc[v] != scc[u]) continue;
		if (v == f) {f = -1; continue;}
		if (dfn[v] == 0) dfs2(v, u), exor[u] ^= exor[v];
		else if (instk[v]) {
			ull tmp = rnd(); etmp[tmp] = {u, v};
			exor[u] ^= tmp; exor[v] ^= tmp;
		}
	}
	instk[u] = 0;
}
set<pair<int, int> > bann;
void dfs3(int u, int f) {
	dfn[u] = 2; for (int v : G[u]) {
		if (scc[v] != scc[u]) continue;
		if (v == f) {f = -1; continue;}
		if (dfn[v] == 1) {
			set<int> resv; dfs3(v, u);
			if (etmp.find(exor[v]) != etmp.end()) {
				bann.insert({u, v}); bann.insert({v, u});
				auto x = etmp[exor[v]]; bann.insert(x);
				swap(x.first, x.second); bann.insert(x);
			}
			else if (mp.find(exor[v]) != mp.end()) {
				int w = mp[exor[v]];
				bann.insert({u, v}); bann.insert({v, u});
				bann.insert({w, fa[w]}); bann.insert({fa[w], w});
			}
			else mp[exor[v]] = v;
		}
	}
	stk.push(u);
}
vector<vector<int>> ans;
void dfs4(int u, int f, vector<int> &res) {
	res.push_back(u); dfn[u] = 3; for (int v : G[u]) {
		if (scc[v] != scc[u]) continue;
		if (v == f) {f = -1; continue;}
		if (bann.find({u, v}) != bann.end()) continue;
		if (dfn[v] == 2) dfs4(v, u, res);
	}
}
int main() {
	int n, m; scanf("%d %d", &n, &m);
	for (int i = 1; i <= m; i++) {
		int u, v; scanf("%d %d", &u, &v); if (u == v) continue;
		G[u].push_back(v); G[v].push_back(u);
	}
	for (int i = 0; i < n; i++) if (dfn[i] == 0) dfs1(i, i);
	memset(dfn, 0, sizeof dfn);
	for (int i = 0; i < n; i++) if (dfn[i] == 0) dfs2(i, i), dfs3(i, i);
	for (int i = 0; i < n; i++) if (dfn[i] == 2) {
		vector<int> res; dfs4(i, i, res); ans.push_back(res);
	}
	for (auto &x : ans) sort(x.begin(), x.end());
	sort(ans.begin(), ans.end(), [](vector<int> &x, vector<int> &y) {return x[0] < y[0];});
	printf("%d\n", (int)ans.size());
	for (auto &x : ans) {
		printf("%d ", (int)x.size());
		for (auto y : x) printf("%d ", y); puts("");
	}
}