Problem: A permutation is a sequence of integers p1, p2, ..., pn, consisting of n distinct positive integers, each of them doesn't exceed n. Let's denote the i-th element of permutation p as pi. We'll call number n the size of permutation p1, p2, ..., pn.

Nickolas adores permutations. He likes some permutations more than the others. He calls such permutations perfect. A perfect permutation is such permutation p that for any i (1 ≤ i ≤ n) (n is the permutation size) the following equations hold ppi = i and pi ≠ i. Nickolas asks you to print any perfect permutation of size n for the given n.

Input

A single line contains a single integer n (1 ≤ n ≤ 100) — the permutation size.

Output

If a perfect permutation of size n doesn't exist, print a single integer -1. Otherwise print n distinct integers from 1 to n, p1, p2, ..., pn — permutation p, that is perfect. Separate printed numbers by whitespaces.

Examples

Input

1


Output

-1


Input

2


Output

2 1 


Input

4


Output

2 1 4 3 

Solution (in JAVA):

Solution:
import java.util.*;
import java.io.BufferedInputStream;
import java.math.*;
import static java.lang.Math.*;
import static java.lang.Character.*;

public class Main{
	public static void main(String[]args){
		A233 a=new A233();
		a.solve();
	}
}

class IO{

	public static Scanner input=new Scanner(new BufferedInputStream(System.in));

	public static void println(Object o){
		System.out.println(o.toString());
	}

	public static void println(String o){
		System.out.println(o);
	}

	public static void print(Object o){
		System.out.print(o.toString());
	}

	public static void print(String o){
		System.out.print(o);
	}


}

class A96{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	public void solve(){
		while(input.hasNext()){
			String s=input.next();
			s=s.replaceAll("0000000","*");
			s=s.replaceAll("1111111","*");
			if(s.contains("*"))System.out.println("YES");
			else System.out.println("NO");
		}
	}
}

class A112{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	public void solve(){
		String a=input.nextLine();
		String b=input.nextLine();
		if(a.compareToIgnoreCase(b)<0)System.out.println(-1);
		else if(a.compareToIgnoreCase(b)==0)System.out.println(0);
		else System.out.println(1);
	}
}

class A339{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	public void solve(){
		int []a=new int[1000];
		String s=input.nextLine();
		int t=0;
		for(int i=0;i<s.length();i++){
			if(Character.isDigit(s.charAt(i))){
				a[t++]=s.charAt(i)-'0';
			}
		}
		Arrays.sort(a,0,t);
		for(int i=0;i<t-1;i++){
			System.out.print(a[i]+"+");
		}
		System.out.println(a[t-1]);
	}
}

class B508{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	public void solve(){
		StringBuilder s;
		s=new StringBuilder(input.nextLine());
		boolean ok=false;
		int n=s.length();
		int m=s.charAt(n-1)-'0';
		for(int i=0;i<n;i++){
			if(ok)break;
			int t=s.charAt(i)-'0';
			if(t%2==0&&t<m){
				Character tc=s.charAt(i);
				s.setCharAt(i,s.charAt(n-1));
				s.setCharAt(n-1,tc);
				ok=true;
			}
		}

		if(ok){
			System.out.println(s);
		}
		else {
			for(int i=n-2;i>=0;i--){
				int t=s.charAt(i)-'0';
				if(t%2==0){
					Character tc=s.charAt(i);
					s.setCharAt(i,s.charAt(n-1));
					s.setCharAt(n-1,tc);
					ok=true;
					break;
				}
			}
			if(ok)System.out.println(s);
			else System.out.println(-1);
		}
	}
}

class A352{
	Scanner input=new Scanner(new BufferedInputStream(System.in));
	public void solve(){
		int n=input.nextInt();
		int t,t5=0,t0=0;
		for(int i=0;i<n;i++){
			t=input.nextInt();
			if(t==5)t5++;
			if(t==0)t0++;
		}
		if(t0==0)System.out.println(-1);
		else if(t5>=9){
			int tt=t5/9;
			while(tt-->0)
				for(int i=0;i<9;i++)System.out.print(5);
			for(int i=0;i<t0;i++)System.out.print(0);
			System.out.println();
		}
		else System.out.println(0);
	}
}

class A629{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	private int [][]a=new int[105][105];
	private String []s=new String[105];

	public void solve(){
		int n=input.nextInt();
		input.nextLine();
		for(int i=0;i<n;i++){
			s[i]=input.nextLine();
			Arrays.fill(a[i],0);
		}
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(s[i].charAt(j)=='C'){
					a[i][n]++;
					a[n][j]++;
				}
			}
		}
		int ans=0;
		for(int i=0;i<n;i++){
			ans+=a[i][n]*(a[i][n]-1)/2;
			ans+=a[n][i]*(a[n][i]-1)/2;
		}
		System.out.println(ans);
	}
}

class A320{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));

	public void solve(){
		String s=input.nextLine();
		s=s.replaceAll("[^14]","&");
		s=s.replaceAll("144","---");
		s=s.replaceAll("14","--");
		s=s.replaceAll("1","-");
		s=s.replaceAll("[-]","");
		if(s.length()==0)System.out.println("YES");
		else System.out.println("NO");
	}
}

class A38{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));

	public void solve(){
		int n=input.nextInt();
		int []a=new int[105];
		for(int i=0;i<n-1;i++){
			a[i]=input.nextInt();
		}
		int s=input.nextInt();
		int b=input.nextInt();
		int ans=0;
		for(int i=s-1;i<b-1;i++){
			ans+=a[i];
		}
		System.out.println(ans);
	}
}

class A262{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));

	public void solve(){
		int n=input.nextInt();
		int k=input.nextInt();
		int ans=0;
		for(int i=0;i<n;i++){
			Integer a=input.nextInt();
			String s=a.toString();
			int t=0;
			for(int j=0;j<s.length();j++){
				if(s.charAt(j)=='4'||s.charAt(j)=='7')t++;
			}
			if(t<=k)ans++;
		}
		System.out.println(ans);
	}
}

class A525{
	private Scanner input=new Scanner(new BufferedInputStream(System.in));
	private int []key=new int[27];

	public void solve(){

		int ans=0;
		Arrays.fill(key,0);
		int n=input.nextInt();
		input.nextLine();
		String s=input.nextLine();
		for(int i=0;i<s.length();i++){
			if(isUpperCase(s.charAt(i))){
				int tk=s.charAt(i)-'A';
				if(key[tk]>0)key[tk]--;
				else ans++;
			}
			else if(isLowerCase(s.charAt(i))){
				int tk=s.charAt(i)-'a';
				key[tk]++;
			}
		}
		System.out.println(ans);

	}
}

class B545{
	
	public void solve(){
		
		String s1=IO.input.nextLine();
		String s2=IO.input.nextLine();
		StringBuilder s=new StringBuilder("");
		int same=0,dif=0,n=s1.length();
		int a=0,b=0;
		for(int i=0;i<n;i++){
			s.append(" ");
			if(s1.charAt(i)==s2.charAt(i)){
				same++;
				s.setCharAt(i,'1');
			}
			else {
				dif++;
				if(a<=b){
					if(s1.charAt(i)=='1')s.setCharAt(i,'0');
					else s.setCharAt(i,'1');
					a++;
				}
				else {
					if(s2.charAt(i)=='1')s.setCharAt(i,'0');
					else s.setCharAt(i,'1');
					b++;
				}
			}
		}

		if(dif%2==1)IO.println("impossible");
		else System.out.println(s);
	}
}

class A233{
	public void solve(){
		int n=IO.input.nextInt();
		if(n%2==1)System.out.println(-1);
		else {
			for(int i=2;i<=n;i+=2){
				System.out.print(i+" "+(i-1)+" ");
			}
		}
	}
}