// Author: kyEEcccccc

#include <bits/stdc++.h>

using namespace std;

using LL = long long;
using ULL = unsigned long long;

#define F(i, l, r) for (int i = (l); i <= (r); ++i)
#define FF(i, r, l) for (int i = (r); i >= (l); --i)
#define MAX(a, b) ((a) = max(a, b))
#define MIN(a, b) ((a) = min(a, b))
#define SZ(a) ((int)((a).size()) - 1)

const int N = 100005, M = 500005;

int n, m, u[M], v[M];
vector<pair<int, int>> to[N];
int dfn[N], tot_dfn, low[N];
vector<int> sk; bool in_sk[N];
int co[N], tot_co;

void tarjan(int u, int pe)
{
	low[u] = dfn[u] = ++tot_dfn;
	sk.push_back(u); in_sk[u] = 1;
	for (auto ee : to[u])
	{
		int v = ee.first, id = ee.second;
		if (id == pe) continue;
		if (dfn[v] == 0) tarjan(v, id), MIN(low[u], low[v]);
		else if (in_sk[v]) MIN(low[u], dfn[v]);
	}
	if (low[u] == dfn[u])
	{
		++tot_co;
		while (sk.back() != u)
		{
			int v = sk.back(); sk.pop_back();
			in_sk[v] = 0;
			co[v] = tot_co;
		}
		sk.pop_back();
		in_sk[u] = 0;
		co[u] = tot_co;
	}
}

vector<int> vec[N];

signed main(void)
{
	// freopen(".in", "r", stdin);
	// freopen(".out", "w", stdout);
	ios::sync_with_stdio(0), cin.tie(nullptr);

	cin >> n >> m;
	F(i, 1, m)
	{
		cin >> u[i] >> v[i];
		++u[i], ++v[i];
		to[u[i]].emplace_back(v[i], i);
		to[v[i]].emplace_back(u[i], i);
	}

	F(i, 1, n) if (dfn[i] == 0) tarjan(i, 0);

	F(i, 1, n) vec[co[i]].push_back(i);
	cout << tot_co << '\n';
	F(i, 1, tot_co)
	{
		cout << vec[i].size() << ' ';
		F(j, 0, SZ(vec[i])) cout << vec[i][j] - 1 << " \n"[j == SZ(vec[i])];
	}

	return 0;
}