import java.util.*; import java.math.*; import java.text.*; public class Main { private static Scanner sc = new Scanner(System.in); public static void main(String[] args) throws Exception { int ans = 500000000; int s = 1; int e = 1000000000; while (true) { System.out.println("? " + ans); System.out.flush(); int ret = sc.nextInt(); if (ret == 1) { s = ans; } else { e = ans-1; } ans = (s+e)/2+1; if (s == e) { System.out.println("! " + s); } } } }