p = 10 ** 7
print("?", p)

low = 1
hi = 10 ** 6 + 1
while hi - low > 1:
    m = hi + low >> 1
    q = 2 * m - p
    print("?", q)
    r = int(input())
    if (p > m) ^ r:
        low = m
    else:
        hi = m
    p = q
print("!", low)