#include <bits/stdc++.h>
using namespace std;

#define pb emplace_back
#define mp make_pair
#define fi first
#define se second
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(),x.end()
typedef pair<int,int> ii;
typedef long long ll;
typedef unsigned long long ull;
const int INF=1012345678;
const ll LLINF=1012345678012345678LL;
const ll MOD=1000000007;

int n;
vector<int> adj[505];
vector<int> leaf;
bool lf[505];
int memo[505];

bool query(vector<int> v){
	sort(ALL(v));
	v.resize(unique(ALL(v))-v.begin());
	printf("? %d",SZ(v));
	for(int i:v)printf(" %d",i);
	printf("\n");
	fflush(stdout);
	char str[5];
	scanf("%s",str);
	if(str[0]=='Y')return 1;
	return 0;
}

bool query(int idx){
	if(memo[idx]!=-1)return memo[idx];
	vector<int> v;
	for(int i=0;i<=idx;i++)v.pb(leaf[i]);
	memo[idx]=query(v);
	return memo[idx];
}

int main(){
	scanf("%d",&n);
	int a,b;
	for(int i=1;i<n;i++){
		scanf("%d%d",&a,&b);
		adj[a].pb(b);adj[b].pb(a);
	}
	for(int i=1;i<=n;i++){
		if(SZ(adj[i])==1){
			lf[i]=1;
			leaf.pb(i);
		}
	}
	for(int i=1;i<=n;i++){
		if(!lf[i]){
			leaf.pb(i);
		}
	}
	int l=1,r=SZ(leaf)-1;
	while(l<r){
		int m=(l+r)/2;
		if(query(m)){
			r=m;
		}else{
			l=m+1;
		}
	}
	int ans=-1;
	if(l==1){
		if(query({leaf[0],leaf[2]})){
			ans=leaf[0];
		}else{
			ans=leaf[1];
		}
	}else{
		ans=leaf[l];
	}
	printf("! %d\n",ans);
	fflush(stdout);
}