import sequtils,strutils

proc asplit(s : string):seq[string]=
    var
        s2 = newSeqWith(1,"")
    for c in s:
        if c != ' ':
            s2[^1] &= c
        else:
            s2.add("")
    return s2
    
var
    D = stdin.readline.parseInt
    A : seq[int]
    L : string
L = stdin.readline
A = L.asplit.map(parseInt)
for i in countdown(D,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(" ")