n = int(input())
b = list(int(input()) for _ in range(n))
a1 = [1]
for i in range(n):
    if i % 2 == 0:
        a1.append(b[i] - a1[-1])
    else:
        a1.append(a1[-1] - b[i])
a2 = [b[0] - 1]
for i in range(n):
    if i % 2 == 0:
        a2.append(b[i] - a2[-1])
    else:
        a2.append(a2[-1] - b[i])
flg = True
for i in range(n+1):
    if a1[i] <= 0:
        flg = False
        break
if flg:
    print(n+1)
    for i in range(n+1):
        print(a1[i])
    exit()
flg = True
for i in range(n+1):
    if a2[i] <= 0:
        flg = False
        break
if flg:
    print(n+1)
    for i in range(n+1):
        print(a2[i])
    exit()
print(-1)