Problem: An exam for n students will take place in a long and narrow room, so the students will sit in a line in some order. The teacher suspects that students with adjacent numbers (i and i + 1) always studied side by side and became friends and if they take an exam sitting next to each other, they will help each other for sure.

Your task is to choose the maximum number of students and make such an arrangement of students in the room that no two students with adjacent numbers sit side by side.

Input

A single line contains integer n (1 ≤ n ≤ 5000) — the number of students at an exam.

Output

In the first line print integer k — the maximum number of students who can be seated so that no two students with adjacent numbers sit next to each other.

In the second line print k distinct integers a1, a2, ..., ak (1 ≤ ai ≤ n), where ai is the number of the student on the i-th position. The students on adjacent positions mustn't have adjacent numbers. Formally, the following should be true: |ai - ai + 1| ≠ 1 for all i from 1 to k - 1.

If there are several possible answers, output any of them.

Examples

Input

6

Output

6
1 5 3 6 2 4

Input

3


Output

2
1 3

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.StringTokenizer;
import java.util.TreeSet;


public class codeforce_a {

    static class FastScanner{
        BufferedReader s;
        StringTokenizer st;
        
        public FastScanner(){
            st = new StringTokenizer("");
            s = new BufferedReader(new InputStreamReader(System.in));
        }
        
        public FastScanner(File f) throws FileNotFoundException{
            st = new StringTokenizer("");
            s = new BufferedReader (new FileReader(f));
        }
        
        public int nextInt() throws IOException{
            if(st.hasMoreTokens())
                return Integer.parseInt(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextInt();
            }
        }
        
      public double nextDouble() throws IOException{
            if(st.hasMoreTokens())
                return Double.parseDouble(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextDouble();
            }
        }
      
        public long nextLong() throws IOException{
            if(st.hasMoreTokens())
                return Long.parseLong(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextLong();
            }
        }
        
        public String nextString() throws IOException{
            if(st.hasMoreTokens())
                return st.nextToken();
            else{
                st = new StringTokenizer(s.readLine());
                return nextString();
            }
            
        }
        public String readLine() throws IOException{
            return s.readLine();
        }
        
        public void close() throws IOException{
            s.close();
        }
        
    }
      private static FastScanner s = new FastScanner();   
      private static PrintWriter ww = new PrintWriter(new OutputStreamWriter(System.out));
     
      static int mod=1000000000+9;
     public static void main(String[] args) throws IOException 
     {
         int n=s.nextInt();
           TreeSet<Integer> hs = new TreeSet<>();
         StringBuilder sb = new StringBuilder();
         
         
     if(n>=5)
     {  
      
         for(int i=1;i<=n;i++)
         {
             hs.add(i);
         }
         int prev=-1;int ans=0;
         
       //  Collections.reverse(hs);
         
         for(int i=1;i<=n;i=i+2)
         {
             if(prev+1!=i)
             {    
                sb.append(i+" ");
                // System.out.println("..  "+i);
                hs.remove(i);ans++;prev=i;
          
             }
         }
         //System.out.println(" "+hs+" "+prev);
         
         for(int i:hs)
         {
             if(Math.abs(i-prev)!=1)
             {
                 sb.append(i+" ");prev=i;ans++;
             }
         }
         System.out.println(""+ans);
         System.out.println(""+sb.toString());
     }
     else
     {
         if(n==1)
         {
             System.out.println("1");
             System.out.println("1");
         }  
        else if(n==2)
         {
             System.out.println("1");
             System.out.println("1");
         } 
         else if(n==3)
         {
             System.out.println("2");
             System.out.println("1 3");
         } 
         else if(n==4)
         {
             System.out.println("4");
             System.out.println("3 1 4 2");
         } 
         
     }
         s.close();
         ww.close();
     }
     
   
    
}
/*zabardast swappimng of sorting
/*
   Arrays.sort(a, new Comparator<int[]>() {
        @Override
        public int compare(int[] int1, int[] int2)
        {
            Integer number1 = int1[1];
            Integer number2 = int2[1];
            return number1.compareTo(number2);
        }
         });
*/
/*
static final Point getMinMax(int[] array) {
        int min = array[0];
        int max = array[0];
        
        for (int index = 0, size = array.length; index < size; ++index, ++index) {
            int value = array[index];
            
            if (index == size - 1) {
                min = min(min, value);
                max = max(max, value);
            } else {
                int otherValue = array[index + 1];
                
                if (value <= otherValue) {
                    min = min(min, value);
                    max = max(max, otherValue);
                } else {
                    min = min(min, otherValue);
                    max = max(max, value);
                }
            }
        }
        
        return new Point(min, max);
    }
    
*/
/*

/// Demonstrate several Is... methods.
class IsDemo {
public static void main(String args[]) {
char a[] = {'a', 'b', '5', '?', 'A', ' '};
for(int i=0; i<a.length; i++) {
if(Character.isDigit(a[i]))                                   ///check if digit is present in string
System.out.println(a[i] + " is a digit.");
if(Character.isLetter(a[i]))
    System.out.println(num + " in binary: " +
Integer.toBinaryString(num));
System.out.println(num + " in octal: " +
Integer.toOctalString(num));
System.out.println(num + " in hexadecimal: " +
Integer.toHexString(num));
}
}
*/
/*
private static void findSubsets(int array[])
{
  int numOfSubsets = 1 << array.length; 

  for(int i = 0; i < numOfSubsets; i++)
 {
    int pos = array.length - 1;                                /////bitmask to find all sub sets
   int bitmask = i;

   System.out.print("{");
   while(bitmask > 0)
   {
    if((bitmask & 1) == 1)
     System.out.print(array[pos]+",");
    bitmask >>= 1;
    pos--;
   }
   System.out.print("}");
 }
}
*/

/*   no of DIVISORSSSSSS
 public ArrayList<Integer> get(int x){
            ArrayList<Integer> divisors = new ArrayList<>();
            for(int i = 1; i * i <= x; i++){
                if(x % i == 0){
                    divisors.add(i);
                    if(i * i != x){
                        divisors.add( x / i);
                    }
                }
            }
            
*/
/*  //// find sum of multiple of a value below limit// ----> (l*(n+1))/2
  public static long getSequenceSum(long value, long limit) {
long q = (limit - 1) / value;
long ans = ((value*q)*(1+q) )/ 2;
return ans;
}
*/
/*// largest prime factor of a no
 public static long largestPrimeFactor(long n) {

        // largest composite factor must be smaller than sqrt
        long sqrt = (long)Math.ceil(Math.sqrt((double)n));

        long largest = -1;

        for(long i = 2; i <= sqrt; i++) {
            if(n % i == 0) {
                long test = largestPrimeFactor(n/i);
                if(test > largest) {
                    largest = test;
                }
            }
        }

        if(largest != -1) {
            return largest;
        }

        // number is prime
        return n;
    } 
*/
/*    // prime no using sieve of erostheneses
  public static void prime()
{
  boolean[] isPrime = new boolean[100000000+ 1];
         Arrays.fill(isPrime, true);

        // mark non-primes <= N using Sieve of Eratosthenes
        for (int i = 2; i*i <= 100000000; i++)
        {

             if (isPrime[i])
             {
                for (int j = i; i*j <= 100000000; j++) {
                    isPrime[i*j] = false;
                }
            }
        }
}

*/
/*//// largest common sequences
 public String lcs(String str1, String str2)
    {
        int l1 = str1.length();
        int l2 = str2.length();
 
        int[][] arr = new int[l1 + 1][l2 + 1];
 
        for (int i = l1 - 1; i >= 0; i--)
        {
            for (int j = l2 - 1; j >= 0; j--)
            {
                if (str1.charAt(i) == str2.charAt(j))
                    arr[i][j] = arr[i + 1][j + 1] + 1;
                else 
                    arr[i][j] = Math.max(arr[i + 1][j], arr[i][j + 1]);
            }
        }
 
        int i = 0, j = 0;
        StringBuffer sb = new StringBuffer();
        while (i < l1 && j < l2) 
     
 {
            if (str1.charAt(i) == str2.charAt(j)) 
            {
                sb.append(str1.charAt(i));
                i++;
                j++;
            }
            else if (arr[i + 1][j] >= arr[i][j + 1]) 
                i++;
            else
                j++;
        }
        return sb.toString();
    }
 
*/
/*
poe using mod 

long powmod(long a, long b)
{
    long res = 1;
    while(b)
    {
        if(b & 1)
        res = (res * a) % MOD;

        a = (a * a) % MOD;

        b >>= 1;
    }
    return res;
}
*/