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.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.PrintWriter;
	import java.io.Writer;
	import java.util.Arrays;
	import java.util.InputMismatchException;
	import java.util.*;
	import java.io.*;
	import java.math.*;
	public class Main5{

	static class Pair
		{ 
			long x; 
			int y;
			public Pair(long x, int y) 
			{	 
				this.x = x; 
				this.y = y; 
			}	 
		} 
		static class Compare
		{ 
			static void compare(Pair arr[], int n) 
			{ 
				// Comparator to sort the pair according to second element 
				Arrays.sort(arr, new Comparator<Pair>() { 
					@Override public int compare(Pair p1, Pair p2) 
					{ 
						if(p1.x>p2.x)
						{
							return 1;
						}
						else if(p2.x>p1.x)
						{
							return -1;
						}
						else
						{
							if(p1.y>p2.y)
							{
								return 1;
							}
							else if(p1.y<p2.y)
							{
								return -1;
							}
							else
								return 0;
						} 
					} 
				}); 
			} 
		}
		public static long pow(long a, long b)
		{
			long result=1;
			while(b>0)
			{
				if (b % 2 != 0)
				{
					result=(result*a);
					b--;
				} 
				a=(a*a);
				b /= 2;
			}   
			return result;
		}
		public static long fact(long num)
		{
					long value=1;
					int i=0;
					for(i=2;i<num;i++)
					{
						value=((value%mod)*i%mod)%mod;
					}
					return value;
				}
				public static long gcd(long a, long b)
				{
					if (a == 0)
						return b;
					return gcd(b%a, a);
				}
				
				public static long lcm(int a,int b)
				{
					return a * (b / gcd(a, b));
				}
				public static long sum(int h)
				{
					return (h*(h+1)/2);
				}
				public static void dfs(int parent,boolean[] visited)
				{
					ArrayList<Integer> arr=new ArrayList<Integer>();
					arr=graph.get(parent);
					visited[parent]=true;
					for(int i=0;i<arr.size();i++)
					{
						int num=arr.get(i);
						if(visited[num]==false)
						{
							dfs(num,visited);
						}
					}
					ar3.add(parent);
					count++;
				}
				static int count=0;
				static ArrayList<Integer> ar3;
				static long mod=1000000007L;
				static ArrayList<ArrayList<Integer>> graph;
				public static void bfs(int num,boolean[] visited)
				{
					Queue<Integer> q=new LinkedList<>();
					q.add(num);
					visited[num]=true;
					while(!q.isEmpty())
					{
						int x=q.poll();
						ArrayList<Integer> al=graph.get(x);
						for(int i=0;i<al.size();i++)
						{
							int y=al.get(i);
							if(visited[y]==false)
							{
								q.add(y);
								visited[y]=true;
							}
						}
					}
				}
							  
				
				
				public static void main(String args[])throws IOException
				{
				//	InputReader in=new InputReader(System.in);
				//	OutputWriter out=new OutputWriter(System.out);
				//	long a=pow(26,1000000005);
				    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
					ArrayList<Integer> ar=new ArrayList<>();
					ArrayList<Integer> ar1=new ArrayList<>();
					ArrayList<Integer> ar2=new ArrayList<>();
			//		ArrayList<Integer> ar3=new ArrayList<>();
					ArrayList<Integer> ar4=new ArrayList<>();
					TreeSet<Integer> ts1=new TreeSet<>();
					TreeSet<String> pre=new TreeSet<>();
					HashMap<Long,Long> hash=new HashMap<>();
					//HashMap<Long,Integer> hash1=new HashMap<Long,Integer>();
					HashMap<Long,Integer> hash2=new HashMap<Long,Integer>();
				/*	boolean[] prime=new boolean[10001];
					for(int i=2;i*i<=10000;i++)
					{
						if(prime[i]==false)
						{
							for(int j=2*i;j<=10000;j+=i)
							{
								prime[j]=true;
								
							}
						}
					}*/
					int n=i();
					int m=i();
					int[] a=new int[m];
					int[] b=new int[m];
					graph=new ArrayList<>();
					for(int i=0;i<=n;i++)
					{
						graph.add(new ArrayList<>());
					}
					for(int i=0;i<m;i++)
					{
						a[i]=i()-1;
						b[i]=i()-1;
						graph.get(a[i]).add(b[i]);
						graph.get(b[i]).add(a[i]);
					}
					boolean[] visited=new boolean[n];
					int flag=0;
					for(int i=0;i<n;i++)
					{
						if(visited[i]==false)
						{
							ar3=new ArrayList<>();
							count=0;
							dfs(i,visited);
							if(count>3)
							{
								flag=1;
								break;
							}
							if(count==1)
							{
								ar.add(ar3.get(0));
							}
							if(count==2)
							{
								ar1.add(ar3.get(1));
								ar1.add(ar3.get(0));
							}
							else if(count==3)
							{
								ar2.add(ar3.get(0));
								ar2.add(ar3.get(2));
								ar2.add(ar3.get(1));
							}
						}
					}
					if(flag==1 || (ar.size()<ar1.size()/2 && ar1.size()>0))
					{
						pln("-1");
					}
					else
					{
					//	pln(ar1+"");
					//	pln(ar2+"");
					//	pln(ar+"");
						for(int i=0;i<ar2.size();i+=3)
						{
							pln((ar2.get(i)+1)+" "+(ar2.get(i+1)+1)+" "+(ar2.get(i+2)+1));
						}
						int k=0;
						for(int i=0;i<ar1.size();i+=2)
						{
							pln((ar1.get(i)+1)+" "+(ar1.get(i+1)+1)+" "+(ar.get(k)+1));
							k++;
						}
						for(int i=k;i<ar.size();i+=3)
						{
							pln((ar.get(i)+1)+" "+(ar.get(i+1)+1)+" "+(ar.get(i+2)+1));
						}
					}
				}
	
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				/**/
				static InputReader in=new InputReader(System.in);
					static OutputWriter out=new OutputWriter(System.out);
					public static long l()
					{
						String s=in.String();
						return Long.parseLong(s);
					}
					public static void pln(String value)
					{
						System.out.println(value);
					}
					public static int i()
					{
						return in.Int();
					}
					public static String s()
					{
						return in.String();
					}
		}
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			class InputReader {
				 
				private InputStream stream;
				private byte[] buf = new byte[1024];
				private int curChar;
				private int numChars;
				private SpaceCharFilter filter;
			 
				public InputReader(InputStream stream) {
					this.stream = stream;
				}
			 
				public int read() {
					if (numChars== -1)
						throw new InputMismatchException();
					if (curChar >= numChars) {
						curChar = 0;
						try {
							numChars = stream.read(buf);
						} catch (IOException e) {
							throw new InputMismatchException();
						}
						if (numChars <= 0)
							return -1;
					}
					return buf[curChar++];
				}
			 
				public int Int() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					int sgn = 1;
					if (c == '-') {
						sgn = -1;
						c = read();
					}
					int res = 0;
					do {
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = read();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
			 
				public String String() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					StringBuilder res = new StringBuilder();
					do {
						res.appendCodePoint(c);
						c = read();
					} while (!isSpaceChar(c));
					return res.toString();
				}
			 
				public boolean isSpaceChar(int c) {
					if (filter != null)
						return filter.isSpaceChar(c);
					return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
				}
			 
				public String next() {
					return String();
				}
			 
				public interface SpaceCharFilter {
					public boolean isSpaceChar(int ch);
				}
			}
			 
			class OutputWriter {
				private final PrintWriter writer;
			 
				public OutputWriter(OutputStream outputStream) {
					writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
				}
			 
				public OutputWriter(Writer writer) {
					this.writer = new PrintWriter(writer);
				}
			 
				public void print(Object...objects) {
					for (int i = 0; i < objects.length; i++) {
						if (i != 0)
							writer.print(' ');
						writer.print(objects[i]);
					}
				}
			 
				public void printLine(Object...objects) {
					print(objects);
					writer.println();
				}
			 
				public void close() {
					writer.close();
				}
			 
				public void flush() {
					writer.flush();
				}
			 
				}
			 
				class IOUtils {
			 
				public static int[] readIntArray(InputReader in, int size) {
					int[] array = new int[size];
					for (int i = 0; i < size; i++)
						array[i] = in.Int();
					return array;
				}
			 
				}