#!/usr/bin/env luajit
require("utils")

local positions = split(io.open(arg[3]):read("*a"), ",")
foreach(positions, tonumber)
table.sort(positions)

local median = positions[#positions/2]
local cost = 0
for k, v in pairs(positions) do
	cost = cost + math.abs(median - v)
end

print(cost)