public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int k = sc . nextInt ( ) ;
  int [ ] ar = new int [ n ] ;
  int [ ] wake = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) ar [ i ] = sc . nextInt ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) wake [ i ] = sc . nextInt ( ) ;
  int ans = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    ans += ( wake [ i ] == 1 ) ? ar [ i ] : 0 ;
  }
  int cur = 0 , max = 0 ;
  int i = 0 , j = 0 ;
  while ( j <= n ) {
    if ( j < k ) {
      cur += ( wake [ j ] == 0 ) ? ar [ j ] : 0 ;
    }
    else if ( j >= k && j < n ) {
      cur += ( ( wake [ j ] == 0 ) ? ar [ j ] : 0 ) - ( ( wake [ i ] == 0 ) ? ar [ i ] : 0 ) ;
      i ++ ;
    }
    max = Math . max ( max , cur ) ;
    j ++ ;
  }
  System . out . println ( ans + max ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int k = sc . nextInt ( ) ; int [ ] ar = new int [ n ] ; int [ ] wake = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) ar [ i ] = sc . nextInt ( ) ; for ( int i = 0 ; i < n ; i ++ ) wake [ i ] = sc . nextInt ( ) ; int ans = 0 ; for ( int i = 0 ; i < n ; i ++ ) { ans += ( wake [ i ] == 1 ) ? ar [ i ] : 0 ; } int cur = 0 , max = 0 ; int i = 0 , j = 0 ; while ( j <= n ) { if ( j < k ) { cur += ( wake [ j ] == 0 ) ? ar [ j ] : 0 ; } else if ( j >= k && j < n ) { cur += ( ( wake [ j ] == 0 ) ? ar [ j ] : 0 ) - ( ( wake [ i ] == 0 ) ? ar [ i ] : 0 ) ; i ++ ; } max = Math . max ( max , cur ) ; j ++ ; } System . out . println ( ans + max ) ; }
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