#include<bits/stdc++.h>
using namespace std;
constexpr int N=100005;
struct Trajan_EBC
{
    int n,m;
    Trajan_EBC(int _n=0):n(_n),m(0){}
    void init(int _n)
    {
        n=_n,m=0;
        return;
    }
    vector<pair<int,int>>G[N];
    void add_edge(int u,int v)
    {
        m++;
        G[u].emplace_back(v,m);
        G[v].emplace_back(u,m);
        return;
    }
    int dfn[N],low[N],Index;
    bool ins[N];
    stack<int>s;
    int bel[N],tot;
    vector<int>block[N];
    void dfs(int u,int prev)
    {
        dfn[u]=low[u]=++Index;
        ins[u]=true;
        s.push(u);
        for(auto [v,id]:G[u])
        {
            if(id==prev) continue;
            if(!dfn[v])
            {
                dfs(v,id);
                low[u]=min(low[u],low[v]);
            }
            else if(ins[v]) low[u]=min(low[u],dfn[v]);
        }
        if(dfn[u]==low[u])
        {
            tot++;
            block[tot].clear();
            while(!s.empty()&&s.top()!=u)
            {
                int v=s.top();
                s.pop();
                ins[v]=false;
                bel[v]=tot;
                block[tot].push_back(v);
            }
            s.pop();
            ins[u]=false;
            bel[u]=tot;
            block[tot].push_back(u);
        }
        return;
    }
    void tarjan()
    {
        fill(dfn+1,dfn+n+1,0);
        fill(low+1,low+n+1,0);
        Index=0;
        fill(bel+1,bel+n+1,0);
        tot=0;
        fill(ins+1,ins+n+1,false);
        for(int i=1;i<=n;i++)
            if(!dfn[i]) dfs(i,0);
        return;
    }
};

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    int n,m;
    cin>>n>>m;
    Trajan_EBC tebc(n);
    for(int i=1;i<=m;i++)
    {
        int u,v;
        cin>>u>>v;
        u++,v++;
        tebc.add_edge(u,v);
    }
    tebc.tarjan();
    int tot=tebc.tot;
    cout<<tot<<"\n";
    for(int i=1;i<=tot;i++)
    {
        int l=tebc.block[i].size();
        cout<<l<<" ";
        for(int u:tebc.block[i])
            cout<<u-1<<" ";
        cout<<"\n";
    }
    return 0;
}