Farmer John's farm consists of a long row of N fields. Each field contains a certain number of cows,.
FJ wants to build a fence around a contiguous group of these fields in order to maximize the average number of cows per field within that block. The block must contain at least F fields, where F given as input.
Calculate the fence placement that maximizes the average, given the constraint.

* Line 1: Two space-separated integers, N and F.
* Lines 2..N+1: Each line contains a single integer, the number of cows in a field. Line 2 gives the number of cows in field 1,line 3 gives the number in field 2, and so on.

* Line 1: A single integer that is 1000 times the maximal average.Do not perform rounding, just print the integer that is .

10 6
6 
4
2
10
3
8
5
9
4
1

6500