def main():
    l,r=-1,10**9+1
    while l+1<r:
        m=(l+r)//2
        print("?", m)
        rep=int(input())
        if rep==1:l=max(m-1,0)
        elif rep==-1:r=max(m-1,1)
        else:
            if m==0:print("! 0")
            else:print("!",m-1)

main()