#include<bits/stdc++.h>
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define pii pair<ll,ll>
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define per(i,a,b) for(ll i=(a);i>=(b);--i)
using namespace std;
bool Mbe;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
void write(ll x){
    if(x<0)putchar('-'),x=-x;
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
const ll N=1e6+9;
ll n,m,hd[N],tot=1,U[N],V[N];
ll dfn[N],low[N],cut[N],tim;
struct Edg{
    ll to,nxt;
}es[N];
void adde(ll x,ll y){
    es[++tot]=(Edg){y,hd[x]};
    hd[x]=tot;
}
void tarjan(ll x,ll lst){
    dfn[x]=low[x]=++tim;
    for(ll i=hd[x];i;i=es[i].nxt){
        if((i^lst)==1)continue;
        ll y=es[i].to;
        if(!dfn[y]){
            tarjan(y,i);
            low[x]=min(low[x],low[y]);
            if(low[y]>dfn[x])cut[i>>1]=1;
        }
        else low[x]=min(low[x],dfn[y]);
    }
}
vector<ll>res[N];
ll cnt,bel[N];
void dfs(ll x){
    bel[x]=cnt;
    res[cnt].push_back(x);
    for(ll i=hd[x];i;i=es[i].nxt){
        ll y=es[i].to;
        if(cut[i>>1])continue;
        if(bel[y])continue;
        dfs(y);
    }
}
bool Med;
int main(){
    cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
    n=read(),m=read();
    rep(i,1,m){
        ll x=read(),y=read();
        x++,y++;
        U[i]=x,V[i]=y;
        adde(x,y),adde(y,x);
    }
    rep(i,1,n){
        if(!dfn[i])tarjan(i,0);
    }
    rep(i,1,n){
        if(!bel[i])cnt++,dfs(i);
    }
    write(cnt),putchar('\n');
    rep(i,1,cnt){
        write(res[i].size()),putchar(' ');
        for(ll x:res[i])write(x-1),putchar(' ');
        putchar('\n');
    }
    return 0;
}