#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 ans;

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

void solve(){
  cout << ans.size() << endl;
  for( int i = 0; i < ans.size(); ++i )
    cout << ans[ i ] << endl;
}

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