import sys
import math

def question(num):
    print("? %d" % num)
    sys.stdout.flush()
    n = int(input())
    return n

def result(num):
    print("! %d" % num)
    sys.stdout.flush()

def first_step(i, max_num, min_num):
    judge = int(max_num / 2)
    
    for i in range(i, 29):
        r = question(judge)
        if r == 1:
            # higer
            min_num = judge
        elif r == -1:
            # low
            max_num = judge
        else:
            return 1000, (judge+i)
        max_num -= 1
        min_num -= 1
        max_num = max_num if max_num >= 0 else 0
        min_num = min_num if min_num >= 0 else 0
        judge = int((max_num - min_num) / 2) + min_num
    return i, min_num

def second_step(i, judge):
    for i in range(i, 100):
        r = question(judge)
        if r == 0:
            break
    return i

# main
max_num = 1e9
judge = int(max_num / 2)
min_num = 10

# less than 100?
r = question(100)
max_num -= 1
min_num -= 1

if r == -1:
    r = second_step(1, min_num)
elif r == 1:
    min_num = 100 - 1
    i, min_num = first_step(1, max_num, min_num)
    if i > 100:
        r = min_num
    else:
        r = second_step(i, min_num)

# 答えを出力
result(r)