Problem: A programming coach has n students to teach. We know that n is divisible by 3. Let's assume that all students are numbered from 1 to n, inclusive.

Before the university programming championship the coach wants to split all students into groups of three. For some pairs of students we know that they want to be on the same team. Besides, if the i-th student wants to be on the same team with the j-th one, then the j-th student wants to be on the same team with the i-th one. The coach wants the teams to show good results, so he wants the following condition to hold: if the i-th student wants to be on the same team with the j-th, then the i-th and the j-th students must be on the same team. Also, it is obvious that each student must be on exactly one team.

Help the coach and divide the teams the way he wants.

Input

The first line of the input contains integers n and m (3 ≤ n ≤ 48, <image>. Then follow m lines, each contains a pair of integers ai, bi (1 ≤ ai < bi ≤ n) — the pair ai, bi means that students with numbers ai and bi want to be on the same team.

It is guaranteed that n is divisible by 3. It is guaranteed that each pair ai, bi occurs in the input at most once.

Output

If the required division into teams doesn't exist, print number -1. Otherwise, print <image> lines. In each line print three integers xi, yi, zi (1 ≤ xi, yi, zi ≤ n) — the i-th team. 

If there are multiple answers, you are allowed to print any of them.

Examples

Input

3 0


Output

3 2 1 


Input

6 4
1 2
2 3
3 4
5 6


Output

-1


Input

3 3
1 2
2 3
1 3


Output

3 2 1 

Solution (in JAVA):

Solution:
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.text.*;

public class cf300b {

    static BufferedReader br;
    static Scanner sc;
    static PrintWriter out;

    public static void initA() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
            //br = new BufferedReader(new FileReader("input.txt"));
            sc = new Scanner(System.in);
            //out = new PrintWriter("output.txt");
            out = new PrintWriter(System.out);
        } catch (Exception e) {
        }
    }

    static boolean next_permutation(Integer[] p) {
        for (int a = p.length - 2; a >= 0; --a) {
            if (p[a] < p[a + 1]) {
                for (int b = p.length - 1;; --b) {
                    if (p[b] > p[a]) {
                        int t = p[a];
                        p[a] = p[b];
                        p[b] = t;
                        for (++a, b = p.length - 1; a < b; ++a, --b) {
                            t = p[a];
                            p[a] = p[b];
                            p[b] = t;
                        }
                        return true;
                    }
                }
            }
        }
        return false;
    }

    public static void initB() {
        try {

            br = new BufferedReader(new FileReader("input.txt"));
            sc = new Scanner(new FileReader("input.txt"));
            out = new PrintWriter("output.txt");

        } catch (Exception e) {
        }
    }

    public static String getString() {
        try {
            return br.readLine();
        } catch (Exception e) {
        }
        return "";
    }

    public static Integer getInt() {
        try {
            return Integer.parseInt(br.readLine());
        } catch (Exception e) {
        }
        return 0;
    }

    public static Integer[] getIntArr() {
        try {
            StringTokenizer temp = new StringTokenizer(br.readLine());
            int n = temp.countTokens();
            Integer temp2[] = new Integer[n];
            for (int i = 0; i < n; i++) {
                temp2[i] = Integer.parseInt(temp.nextToken());
            }
            return temp2;
        } catch (Exception e) {
        }
        return null;
    }

    public static Long[] getLongArr() {
        try {
            StringTokenizer temp = new StringTokenizer(br.readLine());
            int n = temp.countTokens();
            Long temp2[] = new Long[n];
            for (int i = 0; i < n; i++) {
                temp2[i] = Long.parseLong(temp.nextToken());
            }
            return temp2;
        } catch (Exception e) {
        }
        return null;
    }

    public static String[] getStringArr() {
        try {
            StringTokenizer temp = new StringTokenizer(br.readLine());
            int n = temp.countTokens();
            String temp2[] = new String[n];
            for (int i = 0; i < n; i++) {
                temp2[i] = (temp.nextToken());
            }
            return temp2;
        } catch (Exception e) {
        }
        return null;
    }

    public static int getMax(Integer[] ar) {
        int t = ar[0];
        for (int i = 0; i < ar.length; i++) {
            if (ar[i] > t) {
                t = ar[i];
            }
        }
        return t;
    }

    public static void print(Object a) {
        System.out.println(a);
    }

    public static void print(String s, Object... a) {
        System.out.printf(s, a);
    }

    public static int nextInt() {
        return sc.nextInt();
    }

    public static double nextDouble() {
        return sc.nextDouble();
    }

    public static void main(String[] ar) {
        initA();
        solve();
        out.flush();
    }

    public static void solve() {
        Integer xxx[] = getIntArr();
        int n = xxx[0], m = xxx[1];


        HashMap<Integer, ArrayList<Integer>> nah = new HashMap<Integer, ArrayList<Integer>>();

        int grup = 1;

        int dat[] = new int[n + 1];

        for (int i = 0; i <= n; i++) {
            dat[i] = -1;
        }
        for (int i = 0; i < m; i++) {
            Integer x[] = getIntArr();
            int a = x[0], b = x[1];

            if (dat[a] == -1 && dat[b] == -1) {
                dat[a] = grup;
                dat[b] = grup;
                ArrayList<Integer> p = new ArrayList<Integer>();
                p.add(a);
                p.add(b);
                //print("%d BUAT GRUP BARU, GRUP %d\n",i, grup);
                nah.put(grup, p);
                grup++;
                continue;
            }
            if (dat[a] == -1 && dat[b] != -1) {
                dat[a] = dat[b];
                nah.get(dat[b]).add(a);
                continue;
            }
            if (dat[a] != -1 && dat[b] == -1) {
                dat[b] = dat[a];
                //debugGrup(nah);
                //print(i+" "+dat[a]);
                nah.get(dat[a]).add(b);
                continue;
            }
            if (dat[a] != -1 && dat[b] != -1) {
                if (dat[a] != dat[b]) {
                    print(-1);
                    return;
                }
            }
        }
        int yiha = 1;
        for (int i = 1; i <= n; i++) {
            if (dat[i] == -1) {
                //debugGrup(nah);
                while (nah.get(yiha) != null && nah.get(yiha).size() == 3) {
                    yiha++;
                }
                if (nah.get(yiha) == null) {
                    ArrayList<Integer> p = new ArrayList<Integer>();
                   // print("BIKIN BARU");
                    p.add(i);
                    nah.put(yiha, p);
                } else {
                    nah.get(yiha).add(i);
                }

            }
        }

        boolean isValid = true;
        for (Integer key : nah.keySet()) {
            if (nah.get(key).size() != 3) {
                isValid = false;
            }
        }
        //debugGrup(nah);
        if (!isValid) {
            print(-1);
            return;
        }
        for (Integer key : nah.keySet()) {
            ArrayList<Integer> k = nah.get(key);
            for (int i = 0; i < k.size() - 1; i++) {
                print("%d ", k.get(i));
            }
            print(k.get(2));

        }


    }

    static void debugGrup(HashMap<Integer, ArrayList<Integer>> nah) {
        for (Integer key : nah.keySet()) {
            print("%d : %s\n", key, nah.get(key));
        }
    }
}