#include "iostream" 
using namespace std;

int N;
long long int num[200000];
long long int ans[200001];
long long int MIN=0;

int main() {
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> num[i];
	}
	ans[0] = 1;
	for (int i = 1; i < N + 1; i++) {
		if (i % 2 == 1) {
			ans[i] = num[i - 1] - ans[i - 1];
		}
		else {
			ans[i] = ans[i - 1] - num[i - 1];
		}
		if (ans[i] <= 0) {
			if (((i + 1) / 2) % 2 == 0) {
				if (ans[i] - 1 < MIN)MIN = ans[i] ;
			}
			else {
				cout << "-1\n";
				return 0;
			}
		}
	}
	if (MIN < 0) {
		ans[0] -= MIN;
		ans[0]++;
	}
	if (ans[0] <= 0) {
		cout << "-1\n";
		return 0;
	}
	for (int i = 1; i < N + 1; i++) {
		if (i % 2 == 1) {
			ans[i] = num[i - 1] - ans[i - 1];
		}
		else {
			ans[i] = ans[i - 1] - num[i - 1];
		}
		if (ans[i] <= 0) {
			cout << "-1\n";
			return 0;
		}
	}
	cout << N + 1 << "\n";
	for (int i = 0; i < N + 1; i++) {
		cout << ans[i] << "\n";
	}
	return 0;
}