#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<Int> b(n);
  for(Int i=0;i<n;i++) cin>>b[i];

  using P = pair<Int, Int>;  
  auto sub=[&](P x,P y){
             x.first-=y.first;
             x.second-=y.second;
             return x;
           };

  vector<P> vp(n+1);
  vp[0]=P(1,0);
  for(Int i=0;i<n;i++){
    if(~i&1) vp[i+1]=sub(P(0,b[i]),vp[i]);
    else vp[i+1]=sub(vp[i],P(0,b[i]));        
  }  
  
  const Int INF = 1e18;
  Int l=-INF*2,r=INF*2;
  for(Int i=0;i<=n;i++){
    if(vp[i].first<0){
      chmax(l,vp[i].second-INF);
      chmin(r,vp[i].second-1);
    }else{
      chmax(l,-vp[i].second+1);
      chmin(r,-vp[i].second+INF);
    }    
  }
  if(l>r){
    cout<<-1<<endl;
    return 0;
  }
  
  vector<Int> a(n+1,l);
  for(Int i=0;i<n;i++){
    if(~i&1) a[i+1]=b[i]-a[i];
    else a[i+1]=a[i]-b[i];    
  }
  
  cout<<n+1<<endl;
  for(Int x:a) cout<<x<<endl;
  return 0;
}