import java.util.*;
import java.io.*;
import java.awt.geom.*;
import java.math.*;

public class No0246 {
	
	static final Scanner in = new Scanner(System.in);
	static final PrintWriter out = new PrintWriter(System.out,false);

	static void solve() {
		int l = 1, r = 1_000_000_000;
		for (int i=0; i<100; i++) {
			int m = (l + r)/2;
			out.println("? "+m);
			out.flush();
			int x = in.nextInt();
			if (x == 1) {
				l = m;
			} else {
				r = m;
			}
		}

		out.println("! "+l);
	}

	public static void main(String[] args) {
		long start = System.currentTimeMillis();

		solve();
		out.flush();

		long end = System.currentTimeMillis();
		//trace(end-start + "ms");
		in.close();
		out.close();
	}

	static void trace(Object... o) { System.out.println(Arrays.deepToString(o));}
}