low = 10
high = pow(10, 9)
mid = (low + high) // 2
count = 0
while True:
    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
    print(count)