#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; set<ull> etmp; ull exor[MAXN];
mt19937_64 rnd(time(0));
void dfs2(int u, int f) {
	dfn[u] = 1; instk[u] = 1; 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.insert(tmp);
			exor[u] ^= tmp; exor[v] ^= tmp;
		}
	}
	instk[u] = 0;
}
vector<vector<int>> ans;
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) {
			stk.push(-u-1); dfs3(v, u);
			if (etmp.count(exor[v])) {
				vector<int> res; int y; do {
					y = stk.top(); stk.pop(); if (y >= 0) res.push_back(y);
				} while (y != -u-1);
				ans.push_back(res);
			}
			else if (mp.find(exor[v]) != mp.end()) {
				int w = mp[exor[v]], y; vector<int> res; do {
					y = stk.top(); stk.pop(); if (y > 0) res.push_back(y);
				} while (y != w);
				stk.push(w); res.pop_back(); ans.push_back(res);
			}
			else mp[exor[v]] = v;
		}
	}
	stk.push(u);
}
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);
			vector<int> res; while (stk.empty() == 0) {
				if (stk.top() >= 0) res.push_back(stk.top()); stk.pop();
			}
			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("");
	}
}