21246번 - Chess Tournament 스페셜 저지다국어

Alex organizes a chess tournament in his company. The tournament is a round-robin tournament of $n$ people, and each pair of players will face each other exactly once.

The problem is, there are only $k$ chess boards in the office ($k \le \frac{n}{2}$). So only $k$ games can be played at the same time. Let's call $g$ games, being simultaneously played by $2g$ distinct players, where $1 \le g \le k$, a round.

Your task is to help Alex to set a schedule with a minimal number of rounds.

The input contains two integers $n$ and $k$ ($2 \le n \le 200, 1 \le k \le \frac{n}{2}$) --- the number of players and the number of chess boards.

In the first line output an integer $r$ --- the number of rounds.

Then output $r$ sections, describing rounds. In the first line of each section, output an integer $g$ ($1 \le g \le k$) --- the number of games in this round. Then output $g$ lines with two integers each --- the pairs of players that will play in this round. All these $2g$ integers must be distinct integers from $1$ to $n$.

If there are several possible solutions, output any of them.