//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 922337203685477580LL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

const int N = 1e5+10;

//head

int n;
ll b[N];
ll a[N];
pair<ll, ll> range = make_pair(INT64_MIN, INT64_MAX);

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  rep(i, n) cin >> b[i];
  rep(i, n) {
    if(i&1) {
      a[i+1] = a[i]-b[i];
    }
    else {
      a[i+1] = b[i]-a[i];
    }
  }
  rep(i, n+1) {
    ll aa = (ll)1e18-a[i];
    ll bb = 1-a[i];
    if(i%4 == 0 or i%4 == 3) {
      chmin(range.second, aa);
      chmax(range.first, bb);
    }
    else {
      chmin(range.second, -bb);
      chmax(range.first, -aa);
    }
  }
  if(range.first > range.second) {
    cout << -1 << endl;
    return 0;
  }
  cout << n+1 << endl;
  rep(i, n+1) {
    if(i%4 == 0 or i%4 == 3) {
      cout << a[i] + range.first << '\n';
    }
    else {
      cout << a[i] - range.first << '\n';
    }
  }
}