import sequtils,strutils,strscans,algorithm,math,future,macros
template get*():string = stdin.readLine() #.strip()

let
  D = get().parseInt()
var
  A = get().split().map(parseInt)
for i in countdown(D, 3):
  A[i-2] += A[i]

if A.len >= 3 and A[2] != 0:
  echo 2
  echo A[0..2].mapIt($it).join(" ")
elif A.len >= 2 and A[1] != 0:
  echo 1
  echo A[0..1].mapIt($it).join(" ")
else:
  echo 0
  echo A[0]