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()

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

for i in range(0,29):
    r = question(judge)
    if r == 1:
        # higer
        min_num = judge
    elif r == -1:
        # low
        max_num = judge
    else:
        result(judge + i)
        sys.exit()
    max_num = int(math.fabs(max_num - 1))
    min_num = int(math.fabs(min_num - 1))
    judge = int((max_num - min_num) / 2) + min_num

judge = min_num

for i in range(29,100):
    r = question(judge)
    if r == 0:
        result(judge + i)
        break