#include <bits/stdc++.h>
#define il inline
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
typedef unsigned long long ll;
const int N=5e5+5,mod=48611;
int n,m,fa[N],ck[N],vis[N];ll a[N],b[N],w[N];
vector<pii> e[N];
il void adde(int x,int y,int z){e[x].push_back({y,z});}
mt19937_64 rnd(time(0));
struct MAP{
    vector<pair<ll,int> > f[mod];
    il void add(ll x,int y){int z=x%mod;f[z].push_back({x,y});}
    il void change(ll x,int y){
        int z=x%mod;
        for(auto &it:f[z]) if(it.fi==x) {it.se=y;break;}
    }
    il int get(ll x){
        int z=x%mod;
        for(auto it:f[z]) if(it.fi==x) return it.se;
        return 0;
    }
}mp,to;
void dfs(int x,int pre){
    ll u;vis[x]=1;
    for(auto [y,z]:e[x]){
        if(z==pre) continue;
        if(!vis[y]) fa[z]=x,dfs(y,z),a[x]^=a[y];
        else if(!w[z]) w[z]=rnd(),mp.add(w[z],1),a[x]^=w[z],a[y]^=w[z];
    }
    if(mp.get(a[x])) u=rnd(),b[x]^=u;
    else{
        int y=to.get(a[x]);
        if(y) u=rnd(),b[x]^=u,b[y]^=u,to.change(a[x],x);
        else to.add(a[x],x);
    }
}
vector<int> f[N];int idx,id[N];
void dfs1(int x,int pre){
    for(auto [y,z]:e[x]){
        if(z==pre || fa[z]!=x) continue;
        b[y]^=b[x],dfs1(y,z);
    }
    int u=mp.get(b[x]);
    if(!u) mp.add(b[x],u=++idx);
    f[u].push_back(x);
}
int x,y,z;
int main(){
    //freopen("3edge.in","r",stdin);
    scanf("%d%d",&n,&m);mp.add(0,1);
    for(int i=1;i<=m;++i) scanf("%d%d",&x,&y),++x,++y,adde(x,y,i),adde(y,x,i);
    for(int i=1;i<=n;++i) if(!vis[i]) ck[i]=1,dfs(i,0);
    for(int i=0;i<mod;++i) mp.f[i].clear();
    for(int i=1;i<=n;++i) if(ck[i]) dfs1(i,0);
    printf("%d\n",idx);
    for(int i=1;i<=idx;++i){printf("%d ",f[i].size());for(int x:f[i]) printf("%d ",x-1);puts("");}
    return 0;
}