package yukicoder;

import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long[] b = new long[n + 1];
		for (int i = 0; i < n; ++i) {
			b[i + 1] = sc.nextLong();
		}
		/*
		 * a_0-a_1=b_1 a_1+a_2=b_2 a_2-a_3=b_3 a_3+a_4=b_4
		 * 
		 * a_0=0
		 * 
		 * a_(i+1)=b_i-a_i a_(i+1)=a_i-b_i
		 */

		long[] a = new long[n + 2];
		long min = 1;
		int counter = 0;
		while (true) {
			++counter;
			a[1] = min;
			for (int i = 2; i <= n + 1; ++i) {
				if (i % 2 == 0) {
					a[i] = b[i - 1] - a[i - 1];
				} else {
					a[i] = a[i - 1] - b[i - 1];
				}
				min = Math.min(min, a[i]);
			}
			if (min > 0)
				break;
			if (min < 1) {
				min = 1 - min;
			}
			if (counter > 10) {
				System.out.println(-1);
				return;
			}
		}
		System.out.println(n + 1);
		for (int i = 1; i <= n + 1; ++i) {
			System.out.println(a[i]);
		}
	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}