public static void main ( String [ ] stp ) throws Exception {
  Scanner scan = new Scanner ( System . in ) ;
  PrintWriter pw = new PrintWriter ( System . out ) ;
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  StringTokenizer st = new StringTokenizer ( br . readLine ( ) ) ;
  int n = Integer . parseInt ( st . nextToken ( ) ) , k = Integer . parseInt ( st . nextToken ( ) ) , i , p = 0 ;
  ;
  Integer a [ ] = new Integer [ n ] ;
  st = new StringTokenizer ( br . readLine ( ) ) ;
  long sum = 0 , ans = 0 ;
  for ( i = 0 ;
  i < n ;
  i ++ ) {
    a [ i ] = Integer . parseInt ( st . nextToken ( ) ) ;
    sum += a [ i ] ;
  }
  st = new StringTokenizer ( br . readLine ( ) ) ;
  for ( i = 0 ;
  i < k ;
  i ++ ) {
    p = Integer . parseInt ( st . nextToken ( ) ) - 1 ;
    sum -= a [ p ] ;
    ans += sum * a [ p ] ;
    a [ p ] = 0 ;
  }
  for ( i = 1 ;
  i < n ;
  i ++ ) {
    ans += a [ i ] * a [ i - 1 ] ;
  }
  ans += a [ 0 ] * a [ n - 1 ] ;
  pw . println ( ans ) ;
  pw . flush ( ) ;
}

public static void main ( String [ ] stp ) throws Exception { Scanner scan = new Scanner ( System . in ) ; PrintWriter pw = new PrintWriter ( System . out ) ; BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; StringTokenizer st = new StringTokenizer ( br . readLine ( ) ) ; int n = Integer . parseInt ( st . nextToken ( ) ) , k = Integer . parseInt ( st . nextToken ( ) ) , i , p = 0 ; ; Integer a [ ] = new Integer [ n ] ; st = new StringTokenizer ( br . readLine ( ) ) ; long sum = 0 , ans = 0 ; for ( i = 0 ; i < n ; i ++ ) { a [ i ] = Integer . parseInt ( st . nextToken ( ) ) ; sum += a [ i ] ; } st = new StringTokenizer ( br . readLine ( ) ) ; for ( i = 0 ; i < k ; i ++ ) { p = Integer . parseInt ( st . nextToken ( ) ) - 1 ; sum -= a [ p ] ; ans += sum * a [ p ] ; a [ p ] = 0 ; } for ( i = 1 ; i < n ; i ++ ) { ans += a [ i ] * a [ i - 1 ] ; } ans += a [ 0 ] * a [ n - 1 ] ; pw . println ( ans ) ; pw . flush ( ) ; }
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