#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
N, *B = map(int, read().split())

# %%
A0 = [0] * (N + 1)
A1 = [1] + [0] * N

for i, x in enumerate(B):
    if i % 2 == 0:
        A0[i + 1] = x - A0[i]
        A1[i + 1] = x - A1[i]
    else:
        A0[i + 1] = A0[i] - x
        A1[i + 1] = A1[i] - x


# %%
U = 10 ** 18
left = 1
right = U
for x, y in zip(A0, A1):
    dx = y - x
    if dx == 1:
        L = 1 - x
        R = U - x
    else:
        L = x - U
        R = x - 1
    if left < L:
        left = L
    if right > R:
        right = R


# %%
if left > right:
    print(-1)
    exit()

# %%
A = [0] * (N + 1)
A[0] = left
for i, x in enumerate(B):
    if i % 2 == 0:
        A[i + 1] = x - A[i]
    else:
        A[i + 1] = A[i] - x

print(len(A))
print('\n'.join(map(str, A)))