import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
U = 10 ** 18

N = int(input())
B = [int(input()) for _ in range(N)]

amin = 1
amax = U
for i, b in enumerate(B, 1):
    if i % 2 == 1:
        x = max(1, b - amax)
        y = b - amin
    else:
        x = max(1, amin - b)
        y = amax - b
    if x > y:
        print(-1)
        exit()
    amin = x
    amax = y

ans = [amin]
for i, b in reversed(list(enumerate(B, 1))):
    if i % 2 == 1:
        ans.append(b - ans[-1])
    else:
        ans.append(b + ans[-1])


print(N+1)
print(*ans[::-1], sep="\n")