from collections import deque

def question(X):
    print("?", *[x+1 for x in X])
    return input()

def answer(n):
    print("!", n+1)

N = int(input())
G = [[] for _ in range(N)]
for _ in range(N-1):
    u, v = map(int, input().split())
    u, v = u-1, v-1
    G[u].append(v)
    G[v].append(u)

que = deque()
que.append(0)
color = [-1]*N
color[0] = 0
while que:
    n = que.popleft()
    for v in G[n]:
        if color[v] == -1:
            color[v] = color[n]^1
            que.append(v)

C = -1
if color.count(0) >= color.count(1):
    ans = question([i for i in range(N) if color[i] == 0])
    if ans == "Yes":
        C = 0
    else:
        C = 1
else:
    ans = question([i for i in range(N) if color[i] == 1])
    if ans == "Yes":
        C = 1
    else:
        C = 0

IDX = [i for i in range(N) if color[i] == C]
left = 0
right = len(IDX)
while left+1 < right:
    mid = (left+right)//2
    if question(IDX[left:mid]) == "No":
        left = mid
    else:
        right = mid

answer(IDX[left])