#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< int, int > pii;
typedef vector< pii > vp;
typedef vector< double > vd;
typedef vector< vd > vvd;
typedef vector< string > vs;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int N;
vl B;

void init(){
  cin >> N;
  B = vl( N );
  for( int i = 0; i < N; ++i ){
    cin >> B[ i ];
  }
}

vl lo, hi;

void preprocess(){
  lo = hi = vl( N + 1 );
  lo[ 0 ] = 1;
  hi[ 0 ] = ( ll ) 1e18;
  for( int i = 1; i <= N; ++i ){
    if( i & 1 ){
      lo[ i ] = max( 1LL, B[ i - 1 ] - hi[ i - 1 ] );
      hi[ i ] = min( ( ll ) 1e18, B[ i - 1 ] - lo[ i - 1 ] );
      if( not ( lo[ i ] <= hi[ i ] ) ){
        cout << -1 << endl;
        exit( 0 );
      }
    } else{
      lo[ i ] = max( 1LL, lo[ i - 1 ] - B[ i - 1 ] );
      hi[ i ] = min( ( ll ) 1e18, hi[ i - 1 ] - B[ i - 1 ] );
      if( not ( lo[ i ] <= hi[ i ] ) ){
        cout << -1 << endl;
        exit( 0 );
      }
    }
  }
}

void solve(){
  stack< ll > ans;
  ll p = lo[ N ];
  ans.emplace( p );
  for( int i = N; i > 0; --i ){
    if( ~i & 1 ){
      ll np = p + B[ i - 1 ];
      p = np;
      ans.emplace( p );
    } else{
      ll np = B[ i - 1 ] - p;
      p = np;
      ans.emplace( p );
    }
  }
  cout << N + 1 << endl;
  for( ; not ans.empty(); ans.pop() ){
    cout << ans.top() << endl;
  }
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}