import itertools
import math

n = int(input())
k = int(input())
idxlist = [0] * (n-1)
for i in range(len(idxlist)):
    idxlist[i] = i
    
list_a = [int(input()) for i in range(n)] #n elements
# listの要素の間に縦線を入れるときの組み合わせ
# 組み合わせ数: n-1_C_k-1
# k = 4
combtuple = list(itertools.combinations(idxlist, k-1))
# listの両端に縦線を入れる
res = []
for curtuple in combtuple:
    curlist = list(curtuple)
#     print(curlist)
    curlist.insert(0, -1)
    curlist.insert(len(curlist), n)
#     print(curlist)
    avrlist = []
    for j in range(k):
        listb = list_a[curlist[j]+1 : curlist[j+1]+1]
        avrlist.append(sum(listb) / len(listb))
    res.append(math.ceil(max(avrlist)-min(avrlist)))
    avrlist.clear()
print(max(res))