#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys


def query_answer(answer):
    print("! {answer:d}".format(answer=answer))
    sys.stdout.flush()


def query_question(question):
    print("? {question:d}".format(question=question))
    sys.stdout.flush()
    if int(input()) == 1:
        return True
    else:
        return False


def solve(left, right):
    mid = (left + right) // 2
    result = query_question(mid)
    if result:
        if right == mid or right - mid == 1:
            query_answer(mid)
        else:
            solve(mid, right)
    else:
        solve(left, mid)


if __name__ == "__main__":
    solve(1, 10**9)