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:

// author: Ahmed A.M
import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        //S1 p1 = new S1();   p1.solve();
        //S2 p2 = new S2();   p2.solve();
        //S3 p3 = new S3();   p3.solve();
        //S4 p4 = new S4();   p4.solve();
        //S5 p5 = new S5();   p5.solve();
        //S6 p6 = new S6();   p6.solve();
        //S7 p7 = new S7();   p7.solve();
        //S8 p8 = new S8();   p8.solve();
        //S9 p9 = new S9();   p9.solve();
        //S10 p10 = new S10();    p10.solve();
        //S11 p11 = new S11();    p11.solve();
        //S12 p12 = new S12();    p12.solve();
        //S13 p13 = new S13();    p13.solve(); *  confusing
        //S14 p14 = new S14();    p14.solve();
        //S15 p15 = new S15();    p15.solve();
        //S16 p16 = new S16();    p16.solve();
        //S17 p17 = new S17();    p17.solve();
        //S18 p18 = new S18();    p18.solve(); * without help?
        //S19 p19 = new S19();    p19.solve(); * without set ?
        //S20 p20 = new S20();    p20.solve(); * confusing * Data Types
        //S21 p21 = new S21();    p21.solve(); * confusing and fuzzy thinking
        //S22 p22 = new S22();    p22.solve();
        //S23 p23 = new S23();    p23.solve(); * very annoying problem in very annoying moments
        //S24 p24 = new S24();    p24.solve();
        //S25 p25 = new S25();    p25.solve();
        //S26 p26 = new S26();    p26.solve();
        //S27 p27 = new S27();    p27.solve();
        //S28 p28 = new S28();    p28.solve();
        //S29 p29 = new S29();    p29.solve();
        //S30 p30 = new S30();    p30.solve();
        //S31 p31 = new S31();    p31.solve();
        //S32 p32 = new S32();    p32.solve();
        //S33 p33 = new S33();    p33.solve();
        //S34 p34 = new S34();    p34.solve();
        //S35 p35 = new S35();    p35.solve();
        //S36 p36 = new S36();    p36.solve(); * Repeated mistakes
        //S37 p37 = new S37();    p37.solve();
        //S38 p38 = new S38();    p38.solve();
        //S39 p39 = new S39();    p39.solve(); * Not good
        //S40 p40 = new S40();    p40.solve();
        //S41 p41 = new S41();    p41.solve(); * Observations
        //S42 p42 = new S42();    p42.solve(); * ---
        S43 p43 = new S43();    p43.solve();
    }
}


class S43 {

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