URI Online Judge | 2771

# Average

By Yuri Cardoso Santamarina, UFU 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