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

typedef long long LL;

#define F first
#define S second
#define pii pair<LL, LL>
#define pb push_back
#define debug(x) cerr << #x << "=" << x << endl
#define pq priority_queue
#define inf 0x3f
#define rep(i,a,b) for (int i=a; i < (b); i++)
#define MP make_pair
#define SZ(x) (static_cast<int>(x.size()))
#define MOD 1000000007
#define ALL(x) x.begin(), x.end()
void inc(int &a, int b) {a = (a+b)%MOD;}
void dec(int &a, int b) {a = (a-b+MOD)%MOD;}
int prod(int a,int b) {return LL(a)*LL(b)%MOD;}
int lowbit(int x) {return x&(-x);}

const int maxn = 555;

int n;
int deg[maxn];
vector <int> edge[maxn];

vector <int> leaf, candidate;

int main() {
  // freopen("input.txt","r",stdin);
  cin >> n;
  rep(i, 1, n) {
	int u, v;
	cin >> u >> v;
	edge[u].pb(v);
	edge[v].pb(u);
	deg[u]++;
	deg[v]++;
  }
  /*
  rep(i, 1, n + 1) {
	if (deg[i] == 1) continue;
	cout << "? " << n - 1;
    rep(j, 1, n + 1) if (i != j) cout << " " << j;
    cout << endl;
    cout.flush();
    string s;
    cin >> s;
    if (s == "NO") {
	  cout << "! " << i << endl;
	  cout.flush();
	  return 0;
	}
  }
  // root is a leaf
  
  if (SZ(leaf) == 1) {
	cout << "! " << leaf[0] << endl;
  }
  for (auto it : leaf) {
	cout << "? " << SZ(leaf) - 1;
	for (auto itt : leaf) {
	  if (it == itt) continue;
	  cout << " " << itt;
	}
	cout << endl;
	string s;
	cin >> s;
	if (s == "NO") {
	  cout << "! " << it << endl;
	  return 0;
    }
  }
  */
  //idea: check leaves first, then go through non-leaf node
  rep(i, 1, n + 1) {
	if (deg[i] == 1) leaf.pb(i);
	else candidate.pb(i);
  }
  cout << "? " << SZ(leaf);
  for (auto it : leaf) cout << " " << it;
  cout << endl;
  string s;
  cin >> s;
  if (s == "YES") {
	while (SZ(leaf) > 1) {
	  int mid = SZ(leaf) / 2;
	  cout << "? " << mid;
	  rep(i, 0, mid) cout << " " << leaf[i];
	  cout << endl;
	  string ss; cin >> ss;
	  if (ss == "YES") {
		while (SZ(leaf) > mid) leaf.pop_back();
	  }
	  else {
		vector <int> tmp;
		rep(i, mid, SZ(leaf)) tmp.pb(leaf[i]);
		leaf = tmp;
	  }
	}
	cout << "! " << leaf[0] << endl;
  } else {
	while (SZ(candidate) > 1) {
	  int mid = SZ(candidate)/2;
      cout << "? " << mid + SZ(leaf);
      for (auto it : leaf) cout << " " << it;
      rep(i, 0, mid) cout << " " << candidate[i];
      cout << endl;
      string ss; cin >> ss;
      if (ss == "YES") {
	    while (SZ(candidate) > mid) candidate.pop_back();
      }
      else {
	    vector <int> tmp;
	    rep(i, mid, SZ(candidate)) tmp.pb(candidate[i]);
	    candidate = tmp;
	  }
    }
    cout << "! " << candidate[0] << endl;
  }
  return 0;
}