import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        long max = 1000000000;
        long next = 500000000;
        long min = 0;

        for (int i = 0; i < 100; i++) {
            System.out.println("? " + next);
            System.out.flush();

            if (Integer.parseInt(br.readLine()) == 1) {

                min = next;
                next = next + (int) Math.ceil((max - next) / 2);

                if (max == next) {
                    System.out.println("! " + next);
                    System.out.flush();
                    return;
                }
            } else {
                max = next - 1;
                next = next - (int) ((next - min) / 2);
                if (min == next) {
                    System.out.println("! " + next);
                    System.out.flush();
                    return;
                }
            }
        }
    }
}