import strutils, sequtils, math

var a = newSeq[int64](100010)

proc f(i, n: int, b: seq[int64]): bool =
  if i > n: return true
  if i mod 2 == 0:
    a[i] = a[i-1] - b[i-1]
    if a[i] <= 0 or 10^18 < a[i]: return false
    return f(i+1, n, b)
  else:
    a[i] = b[i-1] - a[i-1]
    if a[i] <= 0 or 10^18 < a[i]: return false
    return f(i+1, n, b)

when isMainModule:
  var
    n = stdin.readLine.parseInt
    b = newSeq[int64](n)

  for i in 0..n-1:
    b[i] = stdin.readLine.parseBiggestInt

  if n == 1:
    if b[0] <= 1: echo "-1"
    else:
      echo 2
      echo 1
      echo b[0] - 1
    quit()

  var
    l: int64 = -1
    u: int64 = b[0]

  while u - l > 1:
    let m: int64 = (u + l) div 2
    a[0] = m
    if f(1, n, b): l = m
    else: u = m

  for i in max(1, l-100)..min(b[0]-1, u+100):
    a[0] = i
    if f(1, n, b):
      echo n+1
      for i in 0..n:
        echo a[i]
        assert(1 <= a[i] and a[i] <= 10^18)
        if i == n: continue
        if i mod 2 == 0:
          assert(a[i] + a[i+1] == b[i])
        else:
          assert(a[i] - a[i+1] == b[i])
      quit()

  echo "-1"