Problem: The only difference between the easy and the hard version is the limit to the number of queries.

This is an interactive problem.

There is an array a of n different numbers. In one query you can ask the position of the second maximum element in a subsegment a[l..r]. Find the position of the maximum element in the array in no more than 20 queries.

A subsegment a[l..r] is all the elements a_l, a_{l + 1}, ..., a_r. After asking this subsegment you will be given the position of the second maximum from this subsegment in the whole array.

Input

The first line contains a single integer n (2 ≤ n ≤ 10^5) — the number of elements in the array.

Interaction

You can ask queries by printing "? l r" (1 ≤ l < r ≤ n). The answer is the index of the second maximum of all elements a_l, a_{l + 1}, ..., a_r. Array a is fixed beforehand and can't be changed in time of interaction.

You can output the answer by printing "! p", where p is the index of the maximum element in the array.

You can ask no more than 20 queries. Printing the answer doesn't count as a query.

After printing a query do not forget to output end of line and flush the output. Otherwise, you will get Idleness limit exceeded. To do this, use:

  * fflush(stdout) or cout.flush() in C++; 
  * System.out.flush() in Java; 
  * flush(output) in Pascal; 
  * stdout.flush() in Python; 
  * see documentation for other languages 



Hacks

To make a hack, use the following test format.

In the first line output a single integer n (2 ≤ n ≤ 10^5). In the second line output a permutation of n integers 1 to n. The position of n in the permutation is the position of the maximum

Example

Input


5

3

4



Output


? 1 5

? 4 5

! 1

Note

In the sample suppose a is [5, 1, 4, 2, 3]. So after asking the [1..5] subsegment 4 is second to max value, and it's position is 3. After asking the [4..5] subsegment 2 is second to max value and it's position in the whole array is 4.

Note that there are other arrays a that would produce the same interaction, and the answer for them might be different. Example output is given in purpose of understanding the interaction.

Solution (in JAVA):

Solution:

import java.util.*;
import java.lang.*;
import java.io.*;

public class feb20 {

//	            ***                          ++                      
//             +=-==+                      +++=-                     
//            +-:---==+                   *+=----=                   
//           +-:------==+               ++=------==                  
//           =-----------=++=========================                
//          +--:::::---:-----============-=======+++====             
//          +---:..:----::-===============-======+++++++++           
//          =---:...---:-===================---===++++++++++         
//          +----:...:-=======================--==+++++++++++        
//          +-:------====================++===---==++++===+++++      
//         +=-----======================+++++==---==+==-::=++**+     
//        +=-----================---=======++=========::.:-+*****    
//       +==::-====================--:  --:-====++=+===:..-=+*****   
//       +=---=====================-...  :=..:-=+++++++++===++*****  
//       +=---=====+=++++++++++++++++=-:::::-====+++++++++++++*****+ 
//      +=======++++++++++++=+++++++============++++++=======+****** 
//      +=====+++++++++++++++++++++++++==++++==++++++=:...  . .+**** 
//     ++====++++++++++++++++++++++++++++++++++++++++-.     ..-+**** 
//     +======++++++++++++++++++++++++++++++++===+====:.    ..:=++++ 
//     +===--=====+++++++++++++++++++++++++++=========-::....::-=++* 
//     ====--==========+++++++==+++===++++===========--:::....:=++*  
//     ====---===++++=====++++++==+++=======-::--===-:.  ....:-+++   
//     ==--=--====++++++++==+++++++++++======--::::...::::::-=+++    
//     ===----===++++++++++++++++++++============--=-==----==+++     
//     =--------====++++++++++++++++=====================+++++++     
//     =---------=======++++++++====+++=================++++++++     
//     -----------========+++++++++++++++=================+++++++    
//     =----------==========++++++++++=====================++++++++  
//     =====------==============+++++++===================+++==+++++ 
//     =======------==========================================++++++

	/*
	 * created by : Nitesh Gupta
	 * 
	 */

	public static void main(String[] args) throws Exception {
		first();
//			sec();
//			third();
//			four();
//			fif();
//			six();
	}

	private static void first() throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int n = Integer.parseInt(scn[0]);
		int sm = ask(1, n);
		int left = ask(1, sm);
		int ans = 1;
		if (left == sm) {
			int st = 1, en = sm - 1;
			while (st <= en) {
				int mid = (st + en) / 2;
				int pos = ask(mid, sm);
				if (pos == sm) {
					ans = mid;
					st = mid + 1;
				} else {
					en = mid - 1;
				}
			}
		} else {
			int st = sm + 1, en = n;
			while (st <= en) {
				int mid = (st + en) / 2;
				int pos = ask(sm, mid);
				if (pos == sm) {
					ans = mid;
					en = mid - 1;
				} else {
					st = mid + 1;
				}
			}

		}
		System.out.println("! " + ans);

		return;
	}

	public static int ask(int l, int r) throws Exception {
		if(l==r)return -1;
		System.out.println("? " + l + " " + r);
		System.out.flush();
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int n = Integer.parseInt(scn[0]);
		return n;
	}

	private static void sec() throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int t = Integer.parseInt(scn[0]);
		StringBuilder sb = new StringBuilder();

		while (t-- > 0) {
			scn = (br.readLine()).trim().split(" ");
			int n = Integer.parseInt(scn[0]);
			long[] arr = new long[n];
			scn = (br.readLine()).trim().split(" ");
			for (int i = 0; i < n; i++) {
				arr[i] = Long.parseLong(scn[i]);
			}

			sb.append("\n");
		}
		System.out.println(sb);
		return;
	}

	private static void third() throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int t = Integer.parseInt(scn[0]);
		StringBuilder sb = new StringBuilder();

		while (t-- > 0) {
			scn = (br.readLine()).trim().split(" ");
			int n = Integer.parseInt(scn[0]);
			long[] arr = new long[n];
			scn = (br.readLine()).trim().split(" ");
			for (int i = 0; i < n; i++) {
				arr[i] = Long.parseLong(scn[i]);
			}

			sb.append("\n");
		}
		System.out.println(sb);
		return;
	}

	private static void four() throws Exception {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int t = Integer.parseInt(scn[0]);
		StringBuilder sb = new StringBuilder();

		while (t-- > 0) {
			scn = (br.readLine()).trim().split(" ");
			int n = Integer.parseInt(scn[0]);
			long[] arr = new long[n];
			scn = (br.readLine()).trim().split(" ");
			for (int i = 0; i < n; i++) {
				arr[i] = Long.parseLong(scn[i]);
			}

			sb.append("\n");
		}
		System.out.println(sb);
		return;
	}

	private static void fif() throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int t = Integer.parseInt(scn[0]);
		StringBuilder sb = new StringBuilder();

		while (t-- > 0) {
			scn = (br.readLine()).trim().split(" ");
			int n = Integer.parseInt(scn[0]);
			long[] arr = new long[n];
			scn = (br.readLine()).trim().split(" ");
			for (int i = 0; i < n; i++) {
				arr[i] = Long.parseLong(scn[i]);
			}

			sb.append("\n");
		}
		System.out.println(sb);
		return;
	}

	private static void six() throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] scn = (br.readLine()).trim().split(" ");
		int t = Integer.parseInt(scn[0]);
		StringBuilder sb = new StringBuilder();

		while (t-- > 0) {
			scn = (br.readLine()).trim().split(" ");
			int n = Integer.parseInt(scn[0]);
			long[] arr = new long[n];
			scn = (br.readLine()).trim().split(" ");
			for (int i = 0; i < n; i++) {
				arr[i] = Long.parseLong(scn[i]);
			}

			sb.append("\n");
		}
		System.out.println(sb);
		return;
	}

	public static void sort(long[] arr) {
		int n = arr.length;
		for (int i = 0; i < n; i++) {
			int idx = (int) Math.random() * n;
			long temp = arr[i];
			arr[i] = arr[idx];
			arr[idx] = temp;
		}
		Arrays.sort(arr);
	}

	public static void print(long[][] dp) {
		for (long[] a : dp) {
			for (long ele : a) {
				System.out.print(ele + " ");
			}
			System.out.println();
		}
	}

}