#include <bits/stdc++.h>

using namespace std;

vector<vector<int>> g, vdccs;

vector<int> dfn, low;

vector<bool> cut;

stack<int> stk;

int tot, rt;

// 求点双连通分量(vDCC)

void tarjan(int u) {

dfn[u] = low[u] = tot++;

stk.push(u);

// 特判一个点的vDCC

if (u == rt && g[u].empty()) {

vdccs.push_back({u});

return;

}

int son = 0;

for (auto v : g[u]) {

if (dfn[v] == -1) {

tarjan(v);

low[u] = min(low[u], low[v]);

// 找到vDCC

if (dfn[u] > low[v]) continue;

son++;

// 找到割点

if (u != rt || son > 1) cut[u] = true;

vdccs.push_back({});

int w;

do {

w = stk.top();

stk.pop();

vdccs.back().push_back(w);

} while (w != v);

vdccs.back().push_back(u);

} else {

low[u] = min(low[u], dfn[v]);

}

}

}

/**

* @brief 使用示例

*

* @note 测试链接: https://www.luogu.com.cn/problem/P8435

*/

int main() {

int n, m;

cin >> n >> m;

g.resize(n);

dfn.resize(n, -1);

low.resize(n, -1);

cut.resize(n);

for (int i = 0; i < m; ++i) {

int u, v;

cin >> u >> v;

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] == -1) tarjan(rt = i);

cout << vdccs.size() << "\n";

for (auto& vdcc : vdccs) {

cout << vdcc.size() << " ";

for (auto u : vdcc) cout << u + 1 << " ";

cout << "\n";

}

return 0;

}