Problem

You are given the sizes of $n$ puzzle pieces and need to distribute exactly $m$ pieces to $m$ students.

Each student must receive one puzzle piece. The unfairness of a distribution is the difference between the largest and the smallest piece chosen.

Your task is to choose $m$ pieces so that this unfairness is as small as possible.

Goal

Return the minimum possible value of:

$\max(selected) - \min(selected)$

among all groups of exactly $m$ pieces.

Input Format

• The first line contains two integers $n$ and $m$.
• The second line contains $n$ integers describing the sizes of the puzzle pieces.

Output Format

• Print one integer: the minimum possible unfairness.

Constraints

• $1 \le m \le n$
• Piece sizes are integers.
• A valid selection always exists.

Hints

• Sort the pieces first.
• After sorting, consider every contiguous block of length $m$ and compute its range.