package main

import (
	"bufio"
	"os"
	"strconv"
	"fmt"
)

func main() {
	sc := NewScanner()

	n := sc.NextInt()
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = sc.NextInt()
	}

	a := make([]int, n + 2)

	a[0] = 1
	low := 1
	high := int(1e18)
	for i := 0; i < n; i++ {
		if i % 2 == 0 {
			// [low,high] -> [max(bi-high,1),bi-low]
			tmp_high := high
			high = b[i] - low
			low = max(b[i] - tmp_high, 1)

		} else {

			// [low,high] -> [max(low-bi,1),high-bi]
			high = high - b[i]
			low = max(low - b[i], 1)

		}
		if low > high {
			fmt.Println(-1)
			return
		}

	}
	fmt.Println(n + 1)
	a[n] = low
	ans := make([]int, n + 1)
	ans[n] = low

	for i := n - 1; i >= 0; i-- {
		if i % 2 == 0 {
			ans[i] = b[i] - ans[i + 1]
		} else {
			ans[i] = b[i] + ans[i + 1]
		}
	}
	for i := 0; i < n + 1; i++ {
		fmt.Println(ans[i])
	}

}

func max(a int, b int) int {
	if a < b {
		return b
	}
	return a
}

type Scanner struct {
	r   *bufio.Reader
	buf []byte
	p   int
}

func NewScanner() *Scanner {
	rdr := bufio.NewReaderSize(os.Stdin, 1000)
	return &Scanner{r:rdr}
}
func (s *Scanner) Next() string {
	s.pre()
	start := s.p
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			break
		}
	}
	result := string(s.buf[start:s.p])
	s.p++
	return result
}
func (s *Scanner) NextLine() string {
	s.pre()
	start := s.p
	s.p = len(s.buf)
	return string(s.buf[start:])
}
func (s *Scanner) NextInt() int {
	v, _ := strconv.Atoi(s.Next())
	return v
}
func (s *Scanner) NextInt64() int64 {
	v, _ := strconv.ParseInt(s.Next(), 10, 64)
	return v
}

func (s *Scanner) NextIntArray() []int {
	s.pre()
	start := s.p
	result := []int{}
	for ; s.p < len(s.buf) + 1; s.p++ {
		if s.p == len(s.buf) || s.buf[s.p] == ' ' {
			v, _ := strconv.ParseInt(string(s.buf[start:s.p]), 10, 0)
			result = append(result, int(v))
			start = s.p + 1
		}
	}

	return result
}
func (s *Scanner) NextInt64Array() []int64 {
	s.pre()
	start := s.p
	result := []int64{}
	for ; s.p < len(s.buf) + 1; s.p++ {
		if s.p == len(s.buf) || s.buf[s.p] == ' ' {
			v, _ := strconv.ParseInt(string(s.buf[start:s.p]), 10, 64)
			result = append(result, v)
			start = s.p + 1
		}
	}
	return result
}

func (s *Scanner) NextMap() map[int]bool {
	s.pre()
	start := s.p
	mp := map[int]bool{}
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			v, _ := strconv.Atoi(string(s.buf[start:s.p]))
			mp[v] = true
			start = s.p + 1
		}
	}
	v, _ := strconv.Atoi(string(s.buf[start:s.p]))
	mp[v] = true

	return mp
}

func (s *Scanner) pre() {
	if s.p >= len(s.buf) {
		s.readLine()
		s.p = 0
	}
}
func (s *Scanner) readLine() {
	s.buf = make([]byte, 0)
	for {
		l, p, e := s.r.ReadLine()
		if e != nil {
			panic(e)
		}
		s.buf = append(s.buf, l...)
		if !p {
			break
		}
	}
}