from sys import stdin,setrecursionlimit#,set_int_max_str_digits
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
#setrecursionlimit(2000000) # これこどふぉだと無理
#set_int_max_str_digits(200010)
mod = 998244353 
ii = lambda :int(stdin.readline())
mi = lambda :map(int,stdin.readline().split())
li = lambda :list(mi())
gmi = lambda :map(lambda x: int(x) - 1, stdin.readline().split())
gi = lambda :list(map(lambda x: 0 if x == "." else 1,input())) # グリッド入力受け取り
py = lambda :print("Yes")
pn = lambda :print("No")
pf = lambda :print("First") 
ps = lambda :print("Second")
pyn = lambda x: print("Yes") if x else print("No")
vec = [(1,0),(-1,0),(0,-1),(0,1)]
vec1 = [(1,0),(1,1),(0,1),(-1,1),(-1,0),(-1,-1),(0,-1),(1,-1)] #8方向
vec2 = [(1,1),(1,0),(0,-1),(-1,-1),(-1,0),(0,1)] # 六角形グリッド
inf = 2*10**18
from collections import defaultdict,deque
from heapq import heappop,heappush


def f(x):
    print("?",x,flush=True)
    return ii()


"""
めも pre,nowで聞く
mid で分割できる


"""

pre = 0 
now = 10**6
l,r = 0,10**6

print("?",0,flush=True)
cnt = 0 
ans = 0
while abs(r-l) > 1:
    cnt += 1
    mid = (pre+now)//2
    # print(l,r)
    # print(pre,now,mid)
    if f(now):
        if pre <= now:
            l = mid 
        else:
            r = mid 
        pre = now
        nxt = (l+r)//2 
        now = now + 2*(nxt-now)
    else:
        if pre <= now:
            r = mid 
        else:
            l = mid 
        pre = now
        nxt = (l+r)//2 
        now = now + 2*(nxt-now)

#     print()
# print(l,r)
# print(pre,now)
# if f(now):
#     print("!",l)
# else:
#     print("!",r)
#print(l,r)
print("!",mid)