# coding:UTF-8
import sys

MOD = 10 ** 9 + 7
INF = float('inf')

# 二分探索
imin = 0
imax = 10 ** 9 + 1

print("? {}".format(99))
check = int(input())

if check == 0:
    print("! {}".format(99))

elif check == -1:
    time = 1
    while True:
        print("? {}".format(0))
        check = int(input())

        if check == 0:
            break

        time += 1

    print("! {}".format(time))

elif check == 1:
    time = 1
    while True:
        imid = imin + (imax - imin) // 2

        print("? {}".format(imid - time))
        check = int(input())

        # 2分探索する。
        if check == 0:
            res = imid
            break
        elif check == 1:
            imin = imid
        else:
            imax = imid

        time += 1

    print("! {}".format(res))