# coding: utf-8

def solve():
    aa = [0]
    pmin = 0
    mmin = 1e18
    for i in range(N):
        if i % 2 == 0:
            aa.append(bb[i] - aa[i])
        else:
            aa.append(aa[i] - bb[i])
    for i in range(N + 1):
        if i % 4 in [1, 2]:
            if mmin > aa[i]:
                mmin = aa[i]
        else:
            if pmin > aa[i]:
                pmin = aa[i]
    if pmin <= 0:
        p = - pmin + 1
    elif mmin <= 0:
        p = mmin - 1
    else:
        p = 0
    s = ""
    for i in range(N + 1):
        if i % 4 in [1, 2]:
            aa[i] -= p
        else:
            aa[i] += p
        if aa[i] <= 0:
            return False
    return "\n".join([str(i) for i in aa])


N = int(input())
bb = [int(input()) for i in range(N)]
s = solve()
if s:
    print(N + 1)
    print(s)
else:
    print(-1)