import java.io.*;
import java.util.*;

class Main {
	
	public static void out (Object o) {
		System.out.println(o);
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		int min = 1 , max = 1000000000;
		
		while (true) {
			int mid = max - min != 1 ? (max + min) / 2 : max;
			if (min == mid && mid == max) {
				out("! " + mid);
				break;
			} else {
				out("? "  + mid);
				//out(min+"~"+max);
			}
			System.out.flush();
			
			int n = Integer.parseInt(br.readLine());
			if (n == 0) {
				max = mid - 1;
			} else {
				min = mid;
			}
		}
	}
}