# -*- coding: utf-8 -*-
"""
No.246 質問と回答
https://yukicoder.me/problems/no/246

"""
import sys
from sys import stdin
input = stdin.readline


def main(args):
    ub = 10**9
    lb = 1

    while ub > lb + 4:
        mid = (ub + lb) // 2
        print('? {}'.format(mid), flush=True)
        res = int(input())
        if res == 0:
            ub = mid
        else:
            lb = mid

    for i in range(lb, ub+2):
        print('? {}'.format(i), flush=True)
        res = int(input())
        if res == 0:
            print('! {}'.format(i-1), flush=True)
            break


if __name__ == '__main__':
    main(sys.argv[1:])