# -*- coding: utf-8 -*
import sys
left = 1
right = 10 ** 9 + 1
while right - left > 1:
    mid = (left + right) // 2
    print("? %d" % mid)
    sys.stdout.flush()
    res = int(input())
    if res:
        left = mid
    else:
        right = mid
print("! %d" % left)
sys.stdout.flush()