LIMIT = 10**6

prev = LIMIT + 1
print("?", prev)

ok, ng = 1, LIMIT + 1
while abs(ok - ng) > 1:
    mid = (ok + ng) // 2
    curr = 2 * mid - prev

    if prev < curr:
        curr -= 1
    else:
        curr += 1

    print("?", curr)

    if (int(input()) == 1) == (prev < curr):
        ok = mid
    else:
        ng = mid

    prev = curr

print("!", ok)