def ask(x):
    print(f"? {x}")
    return int(input())

x = ask(98)
if x == 0:
    ans = 98
elif x == -1:
    for i in range(1, 99):
        if ask(0) == 0:
            ans = i
            break
else:
    l = 0
    r = 10**9 + 1
    t = 1
    while r - l > 1:
        mid = (l + r) // 2
        if ask(max(mid - t, 0)) >= 0:
            l = mid
        else:
            r = mid
        t += 1
    ans = l
print(f"! {ans}")