print("? 99")
S = input()
count = 0

if S == "0":
    print(100)
elif S == "-1":
    while 1:
        print("? 0")
        S = input()
        count += 1
        if S == "0":
            print(count)
else:
    L = 99
    R = int(1e9) + 1
    while 1:
        mid = (L + R) // 2
        print("?", mid - 1 - count)
        S = input()
        if S == "0":
            print(mid)
            break
        elif S == "-1":
            R = mid
        else:
            L = mid
        count += 1