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));

        int grade = Integer.parseInt(br.readLine());

        System.out.println(grade - 1);

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

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

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

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

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

        }

    }
}