local mfl, mce = math.floor, math.ceil
local mod = 998244353
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 modpow(src, pow)
  local res = 1
  while 0 < pow do
    if pow % 2 == 1 then
      res = bmul(res, src)
      pow = pow - 1
    end
    src = bmul(src, src)
    pow = mfl(pow / 2)
  end
  return res
end
local n = io.read("*n")
local b = {}
for i = 1, n do
  b[i] = io.read("*n")
end
local c2 = 0
local bias, change = 0, 0
if b[1] == 1 then
  bias = 1
elseif b[1] == -1 then
  change = change + 1
end
local ret = 1
n = n - 1
for i = 1, n do
  local mul = n + 1 - i
  local div = i
  while mul % 2 == 0 do
    c2 = c2 + 1
    mul = mfl(mul / 2)
  end
  while div % 2 == 0 do
    c2 = c2 - 1
    div = mfl(div / 2)
  end
  if 0 == c2 then
    -- print("!", i)
    if b[i + 1] == 1 then
      bias = 1 - bias
    elseif b[i + 1] == -1 then
      change = change + 1
    end
  else
    if b[i + 1] == -1 then
      ret = (ret + ret) % mod
    end
  end
end
-- print(change, bias)
if change == 0 then
  print(bias)
else
  print(bmul(ret, modpow(2, change - 1)))
end