local mod = 998244353
local mfl = math.floor
local function bmul(x, y)
  local x0, y0 = x % 31596, y % 31596
  local x1, y1 = mfl(x / 31596), mfl(y / 31596)
  return (x1 * y1 * 62863 + (x1 * y0 + x0 * y1) * 31596 + x0 * y0) % mod
end
local function badd(x, y)
  return (x + y) % mod
end

local function badd(x, y) return (x + y) % mod end
local n = io.read("*n")
local a = {}
for i = 1, n do a[i] = io.read("*n") end
local pw = {1}
for i = 2, n do
  pw[i] = badd(pw[i - 1], pw[i - 1])
end

local z = 0
local ans = 0
for i = n - 1, 1, -1 do
  z = badd(z, pw[i])
  ans = badd(ans, bmul(z, badd(a[i], mod - a[n + 1 - i])))
end
print(ans)