from collections import deque
n = int(input())
a_list = [i for i in range(n)]
d = deque(a_list)
a=d.popleft()
b=d.popleft()
print('?',a,b)
i = 0
while i <= n//2:
    x = int(input())
    try:
        if x == a and x == b:
            if x == a:
                print('!',b)
            else:
                print('!',a)
        else:
            a = d.popleft()
            b = d.popleft()
            print('?',a,b)
        i+=1
    except:
        print('!',n-1)
        break