#if IN_LOCAL
import local;
#endif // IN_LOCAL
#include<iostream>
#include<algorithm>
using namespace std;
char s[4];
struct Note
{
	unsigned val, pos;
}note[505];
constexpr const char& s_0 = s[0];
constexpr const unsigned& pos_1 = note[1].pos, & pos_2 = note[2].pos, & pos_3 = note[3].pos;
constexpr Note* const noteP1 = note + 1;
inline constexpr bool NoteComparator(const Note a, const Note b)
{
	return a.val < b.val;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	unsigned n;
	cin >> n;
	for (unsigned i = 1; i <= n; note[i].pos = i, ++i);
	for (unsigned i = 1; i < n; ++i)
	{
		unsigned a, b;
		cin >> a >> b;
		++note[a].val;
		++note[b].val;
	}
	sort(noteP1, noteP1 + n, NoteComparator);
	unsigned l = 1, r = n;
	while (l < r && r > 2)
	{
		const unsigned mid = (l + r) / 2;
		cout << "? " << mid;
		for (unsigned i = 1; i <= mid; cout << ' ' << note[i].pos, ++i);
		cout << endl;
		cin >> s;
		if (s_0 == 'Y')
		{
			r = mid;
		}
		else
		{
			l = mid + 1;
		}
	}
	if (l == 1 && r == 2)
	{
		cout << "? 2 " << pos_2 << ' ' << pos_3 << endl;
		cin >> s;
		cout << "! " << (s_0 == 'Y' ? pos_2 : pos_1);
	}
	else
	{
		cout << "! " << l;
	}
	cout << endl;
	return 0;
}