public static void main ( String [ ] args ) {
  Scanner input = new Scanner ( System . in ) ;
  int n = input . nextInt ( ) ;
  int k = input . nextInt ( ) ;
  int a [ ] = new int [ n ] ;
  int c [ ] = new int [ k ] ;
  long total = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    a [ i ] = input . nextInt ( ) ;
    total += a [ i ] ;
  }
  long ans = 0 ;
  for ( int i = 0 ;
  i < k ;
  i ++ ) {
    c [ i ] = input . nextInt ( ) - 1 ;
    total -= a [ c [ i ] ] ;
    ans += total * a [ c [ i ] ] ;
    a [ c [ i ] ] = 0 ;
  }
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    ans += ( a [ i ] * a [ ( i + 1 ) % n ] ) ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner input = new Scanner ( System . in ) ; int n = input . nextInt ( ) ; int k = input . nextInt ( ) ; int a [ ] = new int [ n ] ; int c [ ] = new int [ k ] ; long total = 0 ; for ( int i = 0 ; i < n ; i ++ ) { a [ i ] = input . nextInt ( ) ; total += a [ i ] ; } long ans = 0 ; for ( int i = 0 ; i < k ; i ++ ) { c [ i ] = input . nextInt ( ) - 1 ; total -= a [ c [ i ] ] ; ans += total * a [ c [ i ] ] ; a [ c [ i ] ] = 0 ; } for ( int i = 0 ; i < n ; i ++ ) { ans += ( a [ i ] * a [ ( i + 1 ) % n ] ) ; } System . out . println ( ans ) ; }
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