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.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Scanner;

import java.util.Stack;

 
public class george
{
    static class Reader
    {
        final private int BUFFER_SIZE = 1 << 16;
        private DataInputStream din;
        private byte[] buffer;
        private int bufferPointer, bytesRead;
 
        public Reader()
        {
            din = new DataInputStream(System.in);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }
 
        public Reader(String file_name) throws IOException
        {
            din = new DataInputStream(new FileInputStream(file_name));
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }
 
        public String readLine() throws IOException
        {
            byte[] buf = new byte[64]; // line length
            int cnt = 0, c;
            while ((c = read()) != -1)
            {
                if (c == '\n')
                    break;
                buf[cnt++] = (byte) c;
            }
            return new String(buf, 0, cnt);
        }
 
        public int nextInt() throws IOException
        {
            int ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do
            {
                ret = ret * 10 + c - '0';
            }  while ((c = read()) >= '0' && c <= '9');
 
            if (neg)
                return -ret;
            return ret;
        }
 
        public long nextLong() throws IOException
        {
            long ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');
            if (neg)
                return -ret;
            return ret;
        }
 
        public double nextDouble() throws IOException
        {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
 
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');
 
            if (c == '.')
            {
                while ((c = read()) >= '0' && c <= '9')
                {
                    ret += (c - '0') / (div *= 10);
                }
            }
 
            if (neg)
                return -ret;
            return ret;
        }
 
        private void fillBuffer() throws IOException
        {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1)
                buffer[0] = -1;
        }
 
        private byte read() throws IOException
        {
            if (bufferPointer == bytesRead)
                fillBuffer();
            return buffer[bufferPointer++];
        }
 
        public void close() throws IOException
        {
            if (din == null)
                return;
            din.close();
        }
    }
    static int min(int []arr,int n) {
    int min=arr[0],k=-1;
    for(int i=0;i<n;i++) {
    	if(min>arr[i]) {
    		k=arr[i];
    	}
    }
    return k;
    }
    static int max(int []arr,int n) {
        int max=arr[0],k=-1;
        for(int i=1;i<n;i++) {
        	if(arr[i]>max) 
        		k=arr[i];
        }
        return k;
        }
static long gcd(long a,long b) {
	if (b==0) return a;
	return gcd(b,a%b);
}
static long lcm(int a,int b) {

	return a*b/gcd(a,b);
}
static int tprime(int n) {
int a=1;
	for(int i=2;i<=n;i++) {
		if(n%i==0) {
			System.out.println(i);
			a++;
		}
	}
	return a;
}
static long fact(int n){    
	long fact1=1;  
	      
	  for(int i=1;i<=n;i++){    
	      fact1=fact1*i;    
	  }   
	  return fact1;
	 }    
static void calculateSpan(int price[], int n, int S[])
{
    
    Stack<Integer> st= new Stack<>();
    st.push(0); 
    
    S[0] = 1;
    for (int i = 1; i < n; i++)
    {
        while (!st.empty() && price[st.peek()] <= price[i])
            st.pop();
        S[i] = (st.empty())? (i + 1) : (i - st.peek());
 
       
        st.push(i);
    }
}
 
static void printArray(int arr[],int n)
{
	for(int i=0;i<n;i++) {
    System.out.print(arr[i]+" ");
    }
	System.out.println();
}
 
    public static void main(String[] args) throws IOException
    {
        Reader s=new Reader();
       int n=s.nextInt();
       if(n==1 || n==2) {
    	   System.out.println(1);
    	   System.out.println(1);
       }
       else if(n==3) {
    	   System.out.println(2);
    	   System.out.println("1 3");
       }
       else {
    	   System.out.println(n);
       for(int i=n;i>=1;i--) {
    	   
    	   if(i%2!=0) 
    		   System.out.print(i+" ");
    	   }
       for(int i=n;i>=1;i--) {
    	   if(i%2==0) 
    		   System.out.print(i+" ");
    	   }
    }	
       }
}