D = int(input())
a = [int(i) for i in input().split()]
for i in range(D,2,-1):
	a[i - 2] += a[i]
	a[i] = 0
ans = 0
for i in range(len(a)):
	if a[i] != 0:
		ans = i
print(ans)
print(' '.join([str(a[i]) for i in range(ans + 1)]))