# coding: utf-8
from itertools import combinations
import math

def II(): return int(input())
def ILI(): return list(map(int, input().split()))
N = II()
K = II()
n = [II() for __ in range(N)]

sum_n = sum(n)
s_n = set(n)
ans = -1
for i in range(1, N - 2):
    for comb_1 in combinations(n, i):
        s_comb_1 = set(comb_1)
        sum_comb_1 = sum(comb_1)
        ave_comb_1 = sum_comb_1 / i
        s_others = s_n - s_comb_1
        for j in range(1, N - i - 2):
            for comb_2 in combinations(s_others, j):
                sum_comb_2 = sum(comb_2)
                ave_comb_2 = sum_comb_2 / j
                sum_comb_3 = sum_n - sum_comb_1 - sum_comb_2
                ave_comb_3 = sum_comb_3 / (N - i - j)
                dif = math.floor(max(ave_comb_1, ave_comb_2, ave_comb_3) - min(ave_comb_1, ave_comb_2, ave_comb_3))
                ans = max(ans, dif)

print(ans)