static void exec ( Scanner in , PrintStream out ) {
  int N = in . nextInt ( ) ;
  int [ ] x = new int [ N ] ;
  int [ ] y = new int [ N ] ;
  for ( int i = 0 ;
  i < N ;
  i += 1 ) {
    x [ i ] = in . nextInt ( ) ;
    y [ i ] = in . nextInt ( ) ;
  }
  double max = 0.0 ;
  for ( int i = 0 ;
  i < N ;
  i += 1 ) {
    for ( int j = i + 1 ;
    j < N ;
    j += 1 ) {
      int dx = x [ i ] - x [ j ] ;
      int dy = y [ i ] - y [ j ] ;
      double len = Math . sqrt ( dx * dx + dy * dy ) ;
      if ( max < len ) {
        max = len ;
      }
    }
  }
  out . printf ( "%.6f%n" , max ) ;
}

static void exec ( Scanner in , PrintStream out ) { int N = in . nextInt ( ) ; int [ ] x = new int [ N ] ; int [ ] y = new int [ N ] ; for ( int i = 0 ; i < N ; i += 1 ) { x [ i ] = in . nextInt ( ) ; y [ i ] = in . nextInt ( ) ; } double max = 0.0 ; for ( int i = 0 ; i < N ; i += 1 ) { for ( int j = i + 1 ; j < N ; j += 1 ) { int dx = x [ i ] - x [ j ] ; int dy = y [ i ] - y [ j ] ; double len = Math . sqrt ( dx * dx + dy * dy ) ; if ( max < len ) { max = len ; } } } out . printf ( " % .6f % n " , max ) ; }
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