from collections import deque

def main(a,b,x):
    num = int(x)
    l.append(num)
    flg = max(l) % 2

    if max(l) == 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('?',max(l)-1)

if __name__ == "__main__":
    l=[]
    print(main(input()))