def question(x):
    print("?", x)
    OUTPUT.append(x)
    if 2 <= len(OUTPUT):
        return int(input())
def answer(a):
    print("!", a)

OUTPUT = []
l, r = 1, 10**6
question(l)
ans = question(r)
if ans == 0:
    r = (l+r)//2
else:
    l = (l+r+1)//2
while l+1 < r:
    p = OUTPUT[-1]
    mid = (l+r)//2
    ans = question(p+(mid-p)*2)
    if ans == 0:
        if OUTPUT[-2] < OUTPUT[-1]:
            r = mid
        else:
            l = mid
    else:
        if OUTPUT[-2] < OUTPUT[-1]:
            l = mid
        else:
            r = mid

question(l)
ans = question(r)
if ans == 0:
    answer(l)
else:
    answer(r)