local n = io.read("*n")
local a = {}
local asum = 0
for i = 1, n do
  a[i] = io.read("*n")
  asum = asum + a[i]
end
if 0 <= asum then
  table.sort(a, function(x, y) return x > y end)
else
  table.sort(a)
end
local x, y = 0, 0
for i = 1, n do
  if i % 2 == 1 then
    x = x + a[i]
  else
    y = y + a[i]
  end
end
print(math.abs(x) - math.abs(y))