# yukicoder No.246 質問と回答

b = 1
t = 10 ** 9

# 二分探索
for _ in range(40):
    if b == t:
        print("! {}".format(b), flush = True)
        break
    else:
        q = (b + t + 1) // 2
        print("? {}".format(q), flush = True)

        if int(input()):
            b = q
        else:
            t = q - 1