import sys

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

def ans(y):
    print("!", y)
    sys.stdout.flush()
    exit()

x = ask(80)
if x == 0:
    ans(80)

elif x == -1:
    for i in range(80):
        if ask(9) == 0:
            ans(9 + i + 1)

else:
    high = 10 ** 9 + 1
    low = 80
    num = 1

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

        num += 1
        if x == -1:
            high = mid

        else:
            low = mid + 1