import sys

def question(num):
    print("? " + str(num))
    sys.stdout.flush()
    n = int(input())
    if n == 1:
        return True
    else:
        return False

def result(num):
    print("! " + str(num))
    sys.stdout.flush()


# main
max_num = 1000000000
judge = int(max_num / 2)
min_num = 1

for i in range(0,29):
    r = question(judge)
    if r == True:
        # higer or equal
        min_num = judge
    else:
        # low
        max_num = judge
    judge = int((max_num - min_num) / 2) + min_num 

judge = min_num

for i in range(0,71):
    r = question(judge)
    if r == True:
        min_num = judge
    else:
        max_num = judge
    if (max_num - min_num) <= 1:
        break
    judge += 1

result(min_num)