import sys
input = sys.stdin.readline
l = 0
r = 10**6
pre = (r-l)//2
print("?", pre, flush=True)
for _ in range(24):
    c = (l+r)//2
    dif = c-pre
    now = c+dif
    if dif==0:
        now += 1
    #print(l, r, pre, now)
    print("?", now, flush=True)
    ret = int(input())
    if ret==-1:
        exit()
    if pre<now:
        if ret==1:
            c = (pre+now+1)//2
            l = c
            pre = now
        else:
            c = (pre+now+1)//2
            r = c-1
            pre = now
    else:
        if ret==1:
            c = (pre+now)//2
            r = c
            pre = now
        else:
            c = (pre+now)//2
            l = c+1
            pre = now
    if l==r:
        break
print("!", l, flush=True)