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:
import java.io.*;
import java.math.*;
import java.util.*;


/**
 *
 * @author Saju
 *
 */

public class Main {

	private static int dx[] = { 1, 0, -1, 0 };
	private static int dy[] = { 0, -1, 0, 1 };

	private static final long INF = Long.MAX_VALUE;
	private static final int INT_INF = Integer.MAX_VALUE;
	private static final long NEG_INF = Long.MIN_VALUE;
	private static final int NEG_INT_INF = Integer.MIN_VALUE;
	private static final double EPSILON = 1e-10;

	private static final int MAX = 3007;
	
	private static final long MOD = 1000000007;

	private static final int MAXN = 10000007;
	private static final int MAXA = 10000009;
	private static final int MAXLOG = 22;

	public static void main(String[] args) throws IOException {

		InputReader in = new InputReader(System.in);
		PrintWriter out = new PrintWriter(System.out);

//		 InputReader in = new InputReader(new FileInputStream("src/test.in"));
//		 PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("src/test.out")));



/*




*/
		
		int n = in.nextInt();
		int m = in.nextInt();
		
		List<Integer> adj[] = new ArrayList[n + 1];
		
		for(int i = 0; i <= n; i++) {
			adj[i] = new ArrayList<Integer>();
		}
		
		for(int i = 0; i < m; i++) {
			int a = in.nextInt();
			int b = in.nextInt();
			adj[a].add(b);
			adj[b].add(a);
		}
		
		boolean[] visited = new boolean[n + 1];
		
		boolean ok = true;
		
		List<Integer> singleT = new ArrayList<>();
		List<Pair> doubleT = new ArrayList<>();
		List<Team> tripleT = new ArrayList<>();
		for(int i = 1; i <= n; i++) {
			if(!visited[i]) {
				List<Integer> list = new ArrayList();
				dfs(i, adj, visited, list);
				if(list.size() == 1) {
					singleT.add(list.get(0));
				}
				else if(list.size() == 2) {
					doubleT.add(new Pair(list.get(0), list.get(1)));
				}
				else if(list.size() == 3) {
					tripleT.add(new Team(list.get(0), list.get(1), list.get(2)));
				}
				else {
					ok = false;
					break;
				}
			}
		}
		
		
		if(ok) {
			StringBuilder sb = new StringBuilder();
			for(Team team : tripleT) {
				sb.append(team.toString() + "\n");
			}
			if(doubleT.size() > singleT.size()) {
				out.println(-1);
			}
			else {
				for(int i = 0; i < doubleT.size(); i++) {
					sb.append(doubleT.get(i) + " " + singleT.get(i) + "\n");
				}
				int rem = singleT.size() - doubleT.size();
				if(rem % 3 == 0) {
					int i = doubleT.size();
					rem = rem / 3;
					for(int j = 0; j < rem; j++) {
						sb.append(singleT.get(i) +  " ");
						sb.append(singleT.get(i + 1) + " ");
						sb.append(singleT.get(i + 2) + "\n");
						i += 3;
					}
					out.print(sb.toString());
				}
				else {
					out.println(-1);
				}
			}
		}
		else {
			out.println(-1);
		}
		
		
		out.flush();
		out.close();
		System.exit(0);
	}
	
	private static void dfs(int u, List<Integer>[] adj, boolean[] visited, List<Integer> list) {
		visited[u] = true;
		list.add(u);
		int res = 0;
		for(int v : adj[u]) {
			if(!visited[v]) {
				dfs(v, adj, visited, list);
			}
		}
	}
	
	private static class Team{
		int a;
		int b;
		int c;
		
		Team(int a, int b, int c){
			this.a = a;
			this.b = b;
			this.c = c;
		}
		@Override
		public String toString() {
			return a + " " + b + " " + c;
		}
	}
	
	private static class Pair{
		int a;
		int b;
		
		Pair(int a, int b){
			this.a = a;
			this.b = b;
		}
		@Override
		public String toString() {
			return a + " " + b;
		}
	}
	
	private static int ceil(int n, int x) {
		int div = n / x;
		if(div * x != n) {
			div++;
		}
		return div;
	}

	private static class Point {
		double x;
		double y;

		Point(double x, double y) {
			this.x = x;
			this.y = y;
		}

		double getDistance(Point p2) {
			Point p1 = this;
			double dx = p1.x - p2.x;
			double dy = p1.y - p2.y;

			return Math.sqrt((dx * dx) + (dy * dy));
		}
	}

	private static int abs(int x) {
		if (x < 0) {
			return -x;
		}
		return x;
	}

	private static long abs(long x) {
		if(x < 0) {
			return -x;
		}
		return x;
	}

	private static int lcm(int a, int b) {
		return (a * b) / gcd(a, b);
	}

	private static int gcd(int a, int b) {
		if (a == 0)
			return b;
		return gcd(b % a, a);
	}

	private static int log(long x, int base) {
		return (int) (Math.log(x) / Math.log(base));
	}

	private static long min(long a, long b) {
		if (a < b) {
			return a;
		}
		return b;
	}

	private static int min(int a, int b) {
		if (a < b) {
			return a;
		}
		return b;
	}

	private static long max(long a, long b) {
		if (a < b) {
			return b;
		}
		return a;
	}

	private static int max(int a, int b) {
		if (a < b) {
			return b;
		}
		return a;
	}

	private static class InputReader {
		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream));
			tokenizer = null;
		}

		public String next() {
			try {
				while (tokenizer == null || !tokenizer.hasMoreTokens()) {
					tokenizer = new StringTokenizer(reader.readLine());

				}
			} catch (IOException e) {
				return null;
			}
			return tokenizer.nextToken();
		}

		public String nextLine() {
			String line = null;
			try {
				tokenizer = null;
				line = reader.readLine();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
			return line;
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public long nextLong() {
			return Long.parseLong(next());
		}

		public boolean hasNext() {
			try {
				while (tokenizer == null || !tokenizer.hasMoreTokens()) {
					tokenizer = new StringTokenizer(reader.readLine());
				}
			} catch (Exception e) {
				return false;
			}
			return true;
		}
	}
}