import sys

def ask(y):
    print("?", y)
    sys.stdout.flush()
    ret = int(input())
    return ret

def ans(y):
    print("!", y)
    sys.stdout.flush()
    return None

if ask(80) == -1:
    for i in range(80):
        if ask(9) == 0:
            print("!", 9 + i + 1)
            sys.stdout.flush()
            exit()

else:
    high = 10 ** 9
    low = 0
    num = 1

    while low < high:
        mid = (low + high) // 2
        x = ask(mid - num)
        if x == 0:
            ans(mid)
            exit()

        elif x == -1:
            high = mid

        else:
            low = mid + 1