package src;

import java.util.*;
class B{
	static Scanner s = new Scanner(System.in);
	public static void main(String[] args) {
		long[]
			out = new long[s.nextInt()+1];
		out[0]=1;
		for(int i=0;i<out.length-1;++i) {
			if(i%2==0) {
				out[i+1]=Integer.parseInt(s.next())-out[i];
			}else {
				out[i+1]=out[i]-Integer.parseInt(s.next());
			}
		}
		boolean f=false;
		for(int i=0;i<out.length;i++)
			f|=(out[i]<=0);
		if(f)
			System.out.println(-1);
		else {
			System.out.println(out.length);
			for(int i=0;i<out.length;i++)
				System.out.println(out[i]);
		}
	}
}