# your code goes here
D=int(input())
a=[int (i) for i in input (). split ()]
while len(a)>3:
    a[-3]+=a[-1]
    a.pop(-1)
 #   print (a)
if a[0]==0 and a[1]==0 and a[2]==0:
    a=[0]
    b="0"
i=len(a)-1
b=""
while i>=0:
    b+=str(a[i])+" "
    i-=1
print (len(a)-1)
print (b)