d = int(input())
a = [int(x) for x in input().split()]

for i in reversed(range(3, len(a))):
    a[i - 2] += a[i]
    a[i] = 0

dd = 0
for i in range(min(4, len(a))):
    if a[i] != 0:
        dd = i
print(dd)
print(' '.join([str(x) for x in a[:dd + 1]]))