n = gets.to_i
k = gets.to_i
a = n.times.map{gets.to_f}
ans = []

a.permutation.each do |arr|
    (0..(n-2)).to_a.combination(k-1).each do |comb|
        cnd = []
        (k-1).times do |i|
            if i == 0
                cnd << (arr[0..(comb[i])].sum / (comb[i] - 0 + 1)).ceil
            else
                cnd << (arr[(comb[i-1]+1)..comb[i]].sum / (comb[i] - comb[i-1])).ceil
                cnd << ((arr[(comb[i]+1)..].sum) / arr[(comb[i]+1)..].count).ceil  if i == k-2
            end
        end
        ans << cnd.max - cnd.min
    end
end

puts ans.max