def ask(k,t):
    print(f"? {k}")
    sys.stdout.flush()
    if DEBUG:
        if X-t < k: return -1
        elif k==X-t: return 0
        return 1
    else:
        return int(input())

def ans(k):
    print(f"! {k}")
    exit()

import sys
DEBUG = 0
if DEBUG: X = 1048576

a = ask(100,0)
if a == 0:
    ans(100)
if a == -1:
    for t in range(1,100):
        a = ask(9,t)
        if a==0:
            ans(t+9)
ng = 100
ok = 10**9+1
for t in range(1,100):
    mid = (ok+ng)//2
    a = ask(mid-t,t)
    if a == -1:
        ok = mid
    elif a == 1:
        ng = mid
    else:
        ans(mid)