import sys

max_num = 1000000000
ck_num = max_num // 2
span = max_num // 2

while True:
    print("?",ck_num)
    ans = int(input())
    span = span // 2
    if ans == 1:
        ck_num += span
    else:
        ck_num -= span
    if span == 1:
        break

print("?", ck_num)
ans = int(input())
if ans == 1:
    print("!", ck_num)
    sys.exit()
else:
    print("!", ck_num)
    sys.exit()