#ifdef __GNUC__
#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#endif

#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>
#include <stdio.h>

#include <sstream>
#include <algorithm>
#include <cmath>

#include <string>
#include <cstring>
#include <vector>
#include <valarray>
#include <array>

#include <queue>
#include <complex>
#include <set>
#include <map>
#include <stack>
#include <list>

#include <cassert>//assert();
#include <fstream>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)

/////////
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
#define PII pair<int,int>
/////////
using namespace::std;

// 最大公約数
template<class T>
inline T gcd(T a, T b){return b == 0 ? a : gcd(b, a % b);}
// 最小公倍数
template<class T>
inline T lcm(T a, T b){return a * b / gcd(a, b);}
////////////////////////////////
vector<ULL> fib;
void makeFib(int N){
	fib = vector<ULL>(N+1);
	fib[1] = 1;
	fib[2] = 1;
	for(int i=3;i<=N;++i){
		fib[i] = fib[i-1]+fib[i-2];
	}
}
inline void solve(){
	int N;
	cin >> N;
	vector<ULL> B(N+1);
	for(int i=1;i<=N;++i){
		cin >> B[i];
	}
	vector<ULL> A(N+2,0);
	ULL A1 = 1;

	A[1] = A1;
	//A1を求める。小さい値からはじめて増やしていく
	for(int i=2;i<=N+1;++i){
		if( (i-1)&1 ){
			if( B[i-1] <= A[i-1] ){//減らす方向。
				A1 += A[i-1]-B[i-1]+1;
				A[i-1]+=A[i-1]-B[i-1]+1;
			}
			A[i] = B[i-1]-A[i-1];
		}else{
			if( A[i-1] <= B[i-1] ){
				A1 += B[i-1]-A[i-1]+1;
				A[i-1] += B[i-1]-A[i-1]+1;
			}
			A[i] = A[i-1]-B[i-1];
		}
	}

	A[1] = A1;//A1からAを作る
	for(int i=2;i<=N+1;++i){
		if( (i-1)&1 ){
			A[i] = B[i-1]-A[i-1];
		}else{
			A[i] = A[i-1]-B[i-1];
		}
	}

	//チェック
	ULL AA,BB;
	for(int i=1;i<=N;++i){
		if(i&1){
			AA = A[i]+A[i+1];
			BB = B[i];
			if( BB != AA || AA < A[i] || AA < A[i+1] ){
				cout << -1 << endl;
				return;
			}
		}
		else{
			AA = A[i]-A[i+1];
			BB = B[i];
			if( BB != AA || A[i+1] >= A[i] ){
				cout << -1 << endl;
				return;
			}
		}
	}
	//出力
	{
		cout << N+1 << '\n';
		for(int i=1;i<=N+1;++i){
			cout << A[i] << '\n';
		}cout << flush;
	}
}

signed main(void){
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	//std::cout << std::fixed;//小数を10進数表示
	//cout << setprecision(16);//小数をいっぱい表示する。16?

	solve();
}