#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
n = int(raw_input())
b = [int(raw_input()) for _ in xrange(n)]
a = [1] + [None] * n

for i in xrange(n):
    if i & 1:
        a[i+1] = a[i] - b[i]
    else:
        a[i+1] = b[i] - a[i]

if any(x <= 0 for x in a):
    print -1
else:
    print len(a)
    print '\n'.join(map(str, a))