#include <bits/stdc++.h>
using namespace std;
#define endl '\n'

// #define int long long
const int M = 5e6 + 5, mod = 998244353;

int c, dfn[M], low[M], head[M], cnt, belong[M];
struct dian
{
    int from, to, ne;
} f[M];
vector<int> p[M];
void add(int x, int y)
{
    f[++c].to = y;
    f[c].from = x;
    f[c].ne = head[x];
    head[x] = c;
}
void dfs(int now, int fa)
{
    dfn[now] = low[now] = ++cnt;
    for (int i = head[now]; i; i = f[i].ne)
    {
        int to = f[i].to;
        if (!dfn[to])
            dfs(to, now);
        else if (fa != to)
            low[now] = min(low[now], dfn[to]);
    }
    low[fa] = min(low[fa], low[now]);
}
vector<int> edge[M];
void dfss(int start, int now)
{
    belong[now] = start;
    for (auto x : edge[now])
    {
        if (belong[x])
            continue;
        dfss(start, x);
    }
}

void solve()
{
    int n, m, V;
    cin >> n >> m;
    // vector<int> a(n + 2);
    // for (int i = 1; i <= n; i++)
    //     cin >> a[i];
    while (m--)
    {
        int x, y;
        cin >> x >> y;
        if (x == y)
            continue;
        add(x, y);
        add(y, x);
    }
    for (int i = 1; i <= n; ++i)
        if (!dfn[i])
            dfs(i, i);
    vector<int> vis(c + 2);
    for (int now = 1; now <= n; ++now)
    {
        for (int i = head[now]; i; i = f[i].ne)
        {
            int to = f[i].to;
            if (low[to] > dfn[now])
                vis[i] = 1;
        }
    }
    set<pair<int, int>> s;
    for (int i = 1; i <= c; i += 2)
    {
        int minn = min(f[i].from, f[i].to);
        int maxx = max(f[i].from, f[i].to);
        if ((vis[i] || vis[i + 1]) && s.find({minn, maxx}) == s.end()) // 如果这条边是桥，就跳过
        {
            s.insert(make_pair(minn, maxx));
            continue;
        }
        int x = f[i].from, y = f[i].to;
        edge[x].push_back(y);
        edge[y].push_back(x);
    }
    vector<vector<int>> f(n + 2);
    for (int i = 1; i <= n; ++i)
    {
        if (!belong[i])
            dfss(i, i);
    }
    for (int i = 1; i <= n; ++i)
        f[belong[i]].push_back(i);

    int ans = 0;
    for (int i = 1; i <= n; ++i)
    {
        if (f[i].size() == 0)
            continue;
        ans++;
    }
    cout << ans << endl;
    for (int i = 1; i <= n; ++i)
    {
        if (f[i].size() == 0)
            continue;
        cout << f[i].size() << ' ';
        for (auto j : f[i])
        {
            cout << j << ' ';
        }
        cout << endl;
    }
}
signed main()
{
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
        solve();

    return 0;
}