#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100005, MAXM = 500005;
struct Node
{
    int f, dfn, low, ebcc;
} no[MAXN];
struct Edge
{
    int u, v, next;
} e[MAXM << 1];
int ep = 2;
void connect(int u, int v)
{
    e[ep] = {u, v, no[u].f};
    no[u].f = ep++;
}
int tot = 0;
vector<pair<int, int>> v;
stack<int> s;
vector<int> ebcc[MAXN];
int n1 = 0;
void tarjan(int a, int f)
{
    no[a].dfn = no[a].low = ++tot;
    s.push(a);
    for (int d = no[a].f; d; d = e[d].next)
    {
        if ((d ^ f) == 1)
            continue;
        int b = e[d].v;
        if (no[b].dfn)
            no[a].low = min(no[a].low, no[b].dfn);
        else
        {
            tarjan(b, d);
            no[a].low = min(no[a].low, no[b].low);
        }
    }
    if (no[a].low == no[a].dfn)
    {
        ++n1;
        while (!s.empty())
        {
            int b = s.top();
            s.pop();
            no[b].ebcc = n1;
            ebcc[n1].push_back(b);
            if (b == a)
                break;
        }
    }
}
int main()
{
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int u, v;
        cin >> u >> v;
        connect(u, v);
        connect(v, u);
    }
    for (int i = 0; i < n; i++)
        if (!no[i].dfn)
            tarjan(i, 0);
    cout << n1 << endl;
    for (int i = 1; i <= n1; i++)
    {
        cout << ebcc[i].size() << " ";
        for (auto j : ebcc[i])
            cout << j << " ";
        cout << endl;
    }
    return 0;
}