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 n = Integer.parseInt(br.readLine());
		int n2 = n / 2;
		for (int i = 0; i < n2; i++) {
			int x = i * 2;
			int y = x + 1;
			System.out.println("? " + x + " " + y);
			int z = Integer.parseInt(br.readLine());
			if (z == x) {
				System.out.println("! " + y);
				return;
			}
			if (z == y) {
				System.out.println("! " + x);
				return;
			}
		}
		System.out.println("! " + (n - 1));
		br.close();
	}
}