low = 10
high = pow(10, 9)
mid = (low + high) // 2
count = 0
while True:
    if count < 30:
        print('?', 10 + count)
        if int(input()) == 0:
            print('!', 10 + count + count)
            break
    print('?', mid)
    r = int(input())
    if r == 0:
        print('!', mid + count)
        break
    if r == 1:
        low = mid - 1
    if r == -1:
        high = mid
        low -= 1
    mid = (low + high) // 2
    count += 1