import java.io.*; import java.util.*; import java.util.function.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); for (int i = 0; i < n; i += 2) { System.out.println("? " + i + " " + (i + 1)); System.out.flush(); int x = sc.nextInt(); if (x == i) { System.out.println("! " + (i + 1)); System.out.flush(); return; } else if (x == i + 1) { System.out.println("! " + i); System.out.flush(); return; } } System.out.println("! " + (n - 1)); System.out.flush(); } } class Scanner { BufferedReader br; StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() { try { br = new BufferedReader(new InputStreamReader(System.in)); } catch (Exception e) { } } public int nextInt() { return Integer.parseInt(next()); } public long nextLong() { return Long.parseLong(next()); } public double nextDouble() { return Double.parseDouble(next()); } public String next() { try { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } } catch (Exception e) { e.printStackTrace(); } finally { return st.nextToken(); } } }