#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

using namespace std;
using ll=long long;

// Problem Specific Parameter:

const ll inf=1LL<<60;
ll a[100001];
ll b[100000];

int main(void){
	int n;
	cin >> n;

	rep(i,n) cin >> b[i];
	ll low=1LL,high=inf;

	rep(i,n){
		ll nlow,nhigh;
		// K=b[i]
		if(i%2==0){
			// [low,high] -> [K-high,K-low]
			nlow=max(b[i]-high,1LL),nhigh=b[i]-low;
		}else{
			// [low,high] -> [low-K,high-K]
			nlow=max(low-b[i],1LL),nhigh=high-b[i];
		}
		low=nlow,high=nhigh;
	}

	if(low>high){
		puts("-1");
		return 0;
	}

	// a[n+1]=[low,high] 
	a[n]=low;

	rrep(i,n){
		if(i%2==0)
			a[i]=b[i]-a[i+1];
		else
			a[i]=b[i]+a[i+1];
	}


	cout << n+1 << endl;
	rep(i,n+1) cout << a[i] << endl;

	return 0;
}