#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int n;
vl a;

int main(){
	cin>>n;
	a=vl(n);
	ll l=1,r=INF;
	for(int i=0;i<n;i++){
		ll A,L,R;
		cin>>A;
		a[i]=A;
		if(i%2==0){
			L=max(1ll,A-r);
			R=A-l;
		}
		else{
			L=max(1ll,l-A);
			R=r-A;
		}
		l=L;r=R;
	}
	if(r<l){
		cout<<-1<<endl;
		return 0;
	}
	vl b(n+1);
	b[n]=l;
	for(int i=n-1;i>=0;i--){
		if(i%2==0) b[i]=a[i]-b[i+1];
		else b[i]=a[i]+b[i+1];
	}
	cout<<n+1<<endl;
	for(auto i:b) cout<<i<<endl;
}