N = int(input())

if N % 2 == 1:
    s = set()
    for i in range(N):
        if i not in s:
            print("?",i,i)
            a = int(input())
            if a == i:
                print("!",a)
                break
            else:
                s.add(a)
                s.add(i)
else:
    print("? 0 0")
    a = int(input())
    now = a
    for _ in range(N // 2 - 1):
        print("?",a,now)
        now = int(input())
    print("!",now)