from collections import deque

def main(x):
    num = int(x)
    num_list = [num for i in range(num)]
    p = deque(num_list)
    p_ = p.pop()
    if p_ == num:
        a_list = [i for i in range(num)]
        d = deque(a_list)
        return print('?',0,1)
    else:
        try:
            a=d.popleft()
            b=d.popleft()
            if x == a or x == b:
                if x == a:
                    return print('!',b)
                else:
                    return print('!',a)
            else:
                return print('?',a+2,b+2)
        except:
            return print('?',p_-1)

if __name__ == "__main__":
    print(main(input()))