#region Header
#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
from queue import PriorityQueue
import bisect
import heapq

def input():
    return sys.stdin.readline()[:-1]

sys.setrecursionlimit(1000000)
#endregion

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)



def main():
    l = 1
    r = 10**9+1
    while True:
        mid = (l + r) // 2
        print(f'? {mid}')
        sys.stdout.flush()
        a = int(input())
        if a == 0:
            r = mid
        else:
            l = mid
        if abs(l - r) <= 1:
            print(f'! {l}')
            return


if __name__ == '__main__':
    main()