#include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#define ll long long int
using namespace std;

int main(void){

  ll n;
  ll a[111111],b[111111];
  ll l,r,l2;
  int i;
  cin>>n;
  for(i=1;i<=n;i++){
    cin>>b[i];
  }
  l=(ll)1;
  r=b[1]-1;

  for(i=1;i<=n;i++){
    if(i%2) {
      l2=max(b[i]-r,(ll)1);
      r=b[i]-l;
      l=l2;
    }
    else{
      l=max(l-b[i],(ll)1);
      r=r-b[i];
    }
  }

  if(l>r){
    cout<<"-1\n";
    return 0;
  }
  a[n+1]=l;
  for(i=n;i>=1;i--){
    a[i]=(i%2)?(b[i]-a[i+1]):(b[i]+a[i+1]);
  }
  cout<<n+1<<endl;

  for(i=1;i<=n+1;i++){
    cout<<a[i]<<endl;
  }

  return 0;
}