#include <iostream>
#include <string>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <map>
#include <cmath>
#include <queue>
#include <utility>
#include <functional>
#include <deque>
#include <cctype>
#include <stack>
#include <bitset>
#include <set>

using ll = long long;
using namespace std;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

const ll MOD = 1000000007;
const ll INF = 1 << 30;
const ll INF2 = 9000000000000000000LL;
const double INF3 = 900000000000000;
const int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
const int tx[8] = { -1,0,1,-1,1,-1,0,1 }, ty[8] = { -1,-1,-1,0,0,1,1,1 };
#define ALL(x) (x).begin(),(x).end()


int main() {
	ll n, b[100010], ans[100010];
	cin >> n;
	for (int i = 0;i < n;i++)cin >> b[i];
	ll l = 1, r = INF2;
	for (int i = 0;i < n;i++) {
		ll L = l;
		if (i % 2 == 0) {
			l = max((ll)1, b[i] - r);
			r = b[i] - L;
		}
		else {
			l = max((ll)1, l - b[i]);
			r = r - b[i];
		}
		if (l > r) {
			cout << -1 << endl;
			exit(0);
		}
	}
	ans[n] = r;
	cout << n + 1 << endl;
	for (int i = n - 1;i >= 0;i--) {
		if (i % 2 == 1)ans[i] = ans[i + 1] + b[i];
		else ans[i] = b[i] - ans[i + 1];
	}
	for (int i = 0;i <= n;i++)cout << ans[i] << endl;
}