import java.awt.*;
import java.awt.geom.*;
import java.io.*;
import java.util.*;
class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int lp = 0;
		int rp = 1000000000;
		while(lp <= rp) {
			System.out.println("? " + (lp + rp)/2);
			boolean ans = (sc.nextInt() == 1)?true:false;
			if(ans) {
				lp = (lp + rp)/2+1;
			}
			else {
				rp = (lp + rp)/2-1;
			}
		}
		System.out.println("! " + rp);
	} 	
}