No tag edit access

B. Coach

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputA 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, . Then follow *m* lines, each contains a pair of integers *a*_{i}, *b*_{i} (1 ≤ *a*_{i} < *b*_{i} ≤ *n*) — the pair *a*_{i}, *b*_{i} means that students with numbers *a*_{i} and *b*_{i} want to be on the same team.

It is guaranteed that *n* is divisible by 3. It is guaranteed that each pair *a*_{i}, *b*_{i} occurs in the input at most once.

Output

If the required division into teams doesn't exist, print number -1. Otherwise, print lines. In each line print three integers *x*_{i}, *y*_{i}, *z*_{i} (1 ≤ *x*_{i}, *y*_{i}, *z*_{i} ≤ *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

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Oct/21/2017 18:53:54 (c4).

Desktop version, switch to mobile version.

User lists

Name |
---|