#include <iostream>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
#include <map>
using namespace std;
typedef long long int ll;
const int N=1e6+9,INF=1e9;
const double eps=1e-5;
typedef pair <int,int> PII;
inline int read()
{
    int x=0,f=1;char c=getchar();
    while(c<'0' || c>'9') {if(c=='-') f=-1;c=getchar();}
    while(c>='0' && c<='9') {x=x*10+c-48,c=getchar();}
    return x*f;
}
inline ll readll()
{
    ll x=0,f=1;char c=getchar();
    while(c<'0' || c>'9') {if(c=='-') f=-1;c=getchar();}
    while(c>='0' && c<='9') {x=x*10+c-48,c=getchar();}
    return x*f;
}
struct node{
    int to,nxt;
} edge[N<<1];
int n,m,tot=1,dfn[N],low[N],idx,head[N],color[N],cnt;
bool vis[N<<1];
vector <int> vt[N];
void addedge(int u,int v)
{
    edge[++tot].to=v,edge[tot].nxt=head[u],head[u]=tot;
}
void tarjan(int u,int id)
{
    dfn[u]=low[u]=++idx;
    for(int i=head[u];i;i=edge[i].nxt)
    {
        int v=edge[i].to;
        if(dfn[v]==0)
        {
            tarjan(v,i);
            low[u]=min(low[u],low[v]);
            if(low[v]>dfn[u]) vis[i]=vis[i^1]=true;
        }
        else if(i!=(id^1)) low[u]=min(low[u],dfn[v]);
    }
}
void dfs(int u)
{
    color[u]=cnt,vt[cnt].push_back(u);
    for(int i=head[u];i;i=edge[i].nxt)
    {
        int v=edge[i].to;
        if(vis[i] || color[v]!=0) continue;
        dfs(v);
    }
}
int main()
{
    // #define FILEIO
    #ifdef FILEIO
        freopen("in.in","r",stdin);
        freopen("out.out","w",stdout);
    #endif
    n=read(),m=read();
    for(int i=1;i<=m;i++)
    {
        int u=read()+1,v=read()+1;
        addedge(u,v),addedge(v,u);
    }
    for(int i=1;i<=n;i++)
        if(dfn[i]==0) tarjan(i,0);
    for(int i=1;i<=n;i++)
        if(color[i]==0) ++cnt,dfs(i);
    cout<<cnt<<'\n';
    for(int i=1;i<=cnt;i++)
    {
        cout<<vt[i].size()<<" ";
        for(int j=0;j<vt[i].size();j++) cout<<vt[i][j]-1<<" ";
        puts("");
    }
    cerr<<endl<<1e3*clock()/CLOCKS_PER_SEC<<"ms";
    return 0;
}