#include <bits/stdc++.h>
#define ll long long
#define inf 0x3f3f3f3f
#define re register
#define pii pair<int,int>
#define fi first
#define se second
#define N 502000
using namespace std;
struct edge{
int to,next;
}e[N<<1];
const int mo=1000000007;
inline int read(){
int x=0,w=0;char ch=getchar();
while (!isdigit(ch))w|=ch=='-',ch=getchar();
while (isdigit(ch))x=(x<<1)+(x<<3)+ch-'0',ch=getchar();
return w?-x:x;
}
int n,head[N],cnt,c[N],tot;
pii ed[N];
void add(int u,int v){
e[++cnt].to=v;
e[cnt].next=head[u];
head[u]=cnt;
}
void dfs(int u,int fa){
for (int i=head[u];i;i=e[i].next){
int v=e[i].to;
if (v==fa)continue;
ed[++tot]=(pii){u,v};
dfs(v,u);
}
}
int ck(int l,int r){
int sum=0;
for (int i=1;i<=n;++i)c[i]=0;
for (int i=l;i<=r;++i)c[ed[i].fi]=c[ed[i].se]=1;
for (int i=1;i<=n;++i)sum+=c[i];
cout<<"? "<<sum;
for (int i=1;i<=n;++i)if (c[i])cout<<" "<<i;
cout<<endl;
int x;cin>>x;
return x;
}
signed main(){
n=read();int mx=0;
for (int i=1;i<n;++i){
int u=read(),v=read();
add(u,v);add(v,u);
}
dfs(1,0);
cout<<"? "<<n;
for (int i=1;i<=n;++i)cout<<" "<<i;cout<<endl;
cin>>mx;
int l=1,r=n-1,res;
while (l<=r){
int mid=(l+r)>>1;
if (ck(l,mid)==mx)r=mid-1,res=mid;
else l=mid+1,res=mid+1;
}
cout<<"! "<<ed[res].fi<<" "<<ed[res].se<<endl;
return 0;
}
740A - Alyona and copybooks | 1491A - K-th Largest Value |
922B - Magic Forest | 922D - Robot Vacuum Cleaner |
408B - Garland | 1391A - Suborrays |
1700C - Helping the Nature | 982A - Row |
877A - Alex and broken contest | 919D - Substring |
362B - Petya and Staircases | 1535C - Unstable String |
1738F - Connectivity Addicts | 1342B - Binary Period |
1551C - Interesting Story | 794B - Cutting Carrot |
534B - Covered Path | 1278C - Berry Jam |
1203A - Circle of Students | 1740B - Jumbo Extra Cheese 2 |
1740A - Factorise N+M | 49B - Sum |
23A - You're Given a String | 1105C - Ayoub and Lost Array |
1624E - Masha-forgetful | 998B - Cutting |
250A - Paper Work | 1740C - Bricks and Bags |
1130A - Be Positive | 465A - inc ARG |