URI Online Judge | 2771

Average

By Yuri Cardoso Santamarina, UFU BR Brazil

Timelimit: 1

Joãozinho is finishing his first semester in college and in one of the subjects he will decide his grade, based on the notes of the N tests he did during the semester. The final grade of a student is based on the arithmetic average of 3 different notes. But Joãozinho is not worried about what the highest final grade is, but what K-th highest final grade can be obtained. It is guaranteed that there is a K-th note and remember, it is possible to have more than one final note with the same value and they must be considered different.  

Input

The input contains no more than 10 test cases and ends with EOF.
The first line of a test case contains two integers N and K (\(3 \leq N \leq 100\), \(1 \leq K \leq (N * (N - 1) * (N - 2))/6\)).
The second line contains N integers Ai (\(1 \leq Ai \leq 10^5\)) representing the grade obtained in the i-th test.

Output

The output must contain a floating-point number formatted to one decimal place.

Input Sample Output Sample

4 2
1 2 3 4

2.7