ans_min = 0
ans_max = 10**9
while True:
    ans_half = (ans_min+ans_max)//2
    print("? ",ans_half)
    ans_ans = int(input())
    if ans_ans == 1:
        ans_min = ans_half
    else:
        ans_max = ans_half
    if ans_max - ans_min <= 1:
        print("! ",ans_min)
        exit()