local function lltonumber(str)
  local ret = 0LL
  for i = 1, #str do
    ret = ret * 10LL + str:sub(i, i):byte() - 48
  end
  return ret
end
local function llprint(llnumber)
  local str = tostring(llnumber):gsub("LL", "")
  print(str)
end

local n = io.read("*n", "*l")
local flag = true
local minlim = 1LL
local maxlim = 1000000000000000000LL
local offset = 0LL
local valid = true
local b = {}
for i = 1, n do
  local bs = io.read()
  b[i] = lltonumber(bs)
  if i % 2 == 1 then
    --a[i+1] = b[i] - a[i]
    flag = not flag
    offset = b[i] - offset
  else
    --a[i+1] = a[i] - b[i]
    offset = offset - b[i]
  end
  if flag then
    local ma = 1000000000000000000LL - offset
    if ma < maxlim then
      maxlim = ma
    end
    -- 1 <= offset + x
    if minlim < 1LL - offset then
      minlim = 1LL - offset
    end
  else
    local ma = offset - 1LL
    if ma < maxlim then
      maxlim = ma
    end
    local mi = offset - 1000000000000000000LL
    if minlim < mi then
      minlim = mi
    end
  end
  -- print(i, tostring(minlim), tostring(maxlim), tostring(offset), flag)
  if maxlim < minlim then
    valid = false
  end
end
if valid then
  print(n + 1)
  local v = minlim
  llprint(v)
  for i = 1, n do
    if i % 2 == 1 then
      --a[i+1] = b[i] - a[i]
      v = b[i] - v
    else
      v = v - b[i]
    end
    llprint(v)
  end
else
  print(-1)
end