static int sumFirst ( int a [ ] , int n ) {
  HashMap < Integer , Integer > mp = new HashMap < > ( ) ;
  int suf = 0 ;
  for ( int i = n - 1 ;
  i >= 0 ;
  i -- ) {
    suf += a [ i ] ;
    mp . put ( suf , i ) ;
  }
  int pre = 0 , maxi = - 1 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    pre += a [ i ] ;
    if ( mp . containsKey ( pre ) && mp . get ( pre ) > i ) {
      if ( pre > maxi ) {
        maxi = pre ;
      }
    }
  }
  if ( maxi == - 1 ) return 0 ;
  else return maxi ;
}

static int sumFirst ( int a [ ] , int n ) { HashMap < Integer , Integer > mp = new HashMap < > ( ) ; int suf = 0 ; for ( int i = n - 1 ; i >= 0 ; i -- ) { suf += a [ i ] ; mp . put ( suf , i ) ; } int pre = 0 , maxi = - 1 ; for ( int i = 0 ; i < n ; i ++ ) { pre += a [ i ] ; if ( mp . containsKey ( pre ) && mp . get ( pre ) > i ) { if ( pre > maxi ) { maxi = pre ; } } } if ( maxi == - 1 ) return 0 ; else return maxi ; }
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