public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int [ ] [ ] xy = new int [ 3 ] [ 2 ] ;
  for ( int i = 0 ;
  i < 3 ;
  i ++ ) {
    xy [ i ] [ 0 ] = sc . nextInt ( ) ;
    xy [ i ] [ 1 ] = sc . nextInt ( ) ;
  }
  int xMove = - xy [ 0 ] [ 0 ] ;
  int yMove = - xy [ 0 ] [ 1 ] ;
  for ( int i = 0 ;
  i < 3 ;
  i ++ ) {
    xy [ i ] [ 0 ] += xMove ;
    xy [ i ] [ 1 ] += yMove ;
  }
  out . println ( Math . abs ( xy [ 1 ] [ 0 ] * xy [ 2 ] [ 1 ] - xy [ 1 ] [ 1 ] * xy [ 2 ] [ 0 ] ) / 2.0 ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int [ ] [ ] xy = new int [ 3 ] [ 2 ] ; for ( int i = 0 ; i < 3 ; i ++ ) { xy [ i ] [ 0 ] = sc . nextInt ( ) ; xy [ i ] [ 1 ] = sc . nextInt ( ) ; } int xMove = - xy [ 0 ] [ 0 ] ; int yMove = - xy [ 0 ] [ 1 ] ; for ( int i = 0 ; i < 3 ; i ++ ) { xy [ i ] [ 0 ] += xMove ; xy [ i ] [ 1 ] += yMove ; } out . println ( Math . abs ( xy [ 1 ] [ 0 ] * xy [ 2 ] [ 1 ] - xy [ 1 ] [ 1 ] * xy [ 2 ] [ 0 ] ) / 2.0 ) ; }
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