#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
n = int(raw_input())
b = [int(raw_input()) for _ in xrange(n)]

seed = [1, b[0]//2+1, b[0]//2, b[0]//2-1]

for a0 in seed:
    a = [a0] + [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 all(x > 0 for x in a):
        print len(a)
        print '\n'.join(map(str, a))
        exit(0)

print -1