import sequtils,strutils,strscans

proc scanf(formatstr: cstring)
  {.header: "<stdio.h>", varargs.}


var
    D = stdin.readline.parseInt
    A = newSeq[int](0)
    a : int
    scan = true
for i in 0..D:
    scanf("%d",addr a)
    echo a
    A.add(a)

for i in countdown(A.high,3):
    A[i - 2] += A[i]
    A[i] = 0
var
    D2 : int
    b = newSeq[int](0)
for i in 0..2:
    if A[i] != 0:
        D2 = i
for i in 0..D2:
    b.add(A[i])
echo D2
echo b.join(" ")