public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  List < Integer > x = new ArrayList < > ( ) ;
  List < Integer > y = new ArrayList < > ( ) ;
  IntStream . range ( 0 , n ) . forEach ( i -> {
    x . add ( sc . nextInt ( ) ) ;
    y . add ( sc . nextInt ( ) ) ;
  }
  ) ;
  double maxLen = 0 ;
  for ( int i = 0 ;
  i < x . size ( ) ;
  i ++ ) {
    for ( int j = i + 1 ;
    j < x . size ( ) ;
    j ++ ) {
      double len = Math . sqrt ( Math . pow ( x . get ( j ) - x . get ( i ) , 2 ) + Math . pow ( y . get ( j ) - y . get ( i ) , 2 ) ) ;
      if ( i == 0 && j == 1 || maxLen < len ) {
        maxLen = len ;
      }
    }
  }
  System . out . println ( maxLen ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; List < Integer > x = new ArrayList < > ( ) ; List < Integer > y = new ArrayList < > ( ) ; IntStream . range ( 0 , n ) . forEach ( i -> { x . add ( sc . nextInt ( ) ) ; y . add ( sc . nextInt ( ) ) ; } ) ; double maxLen = 0 ; for ( int i = 0 ; i < x . size ( ) ; i ++ ) { for ( int j = i + 1 ; j < x . size ( ) ; j ++ ) { double len = Math . sqrt ( Math . pow ( x . get ( j ) - x . get ( i ) , 2 ) + Math . pow ( y . get ( j ) - y . get ( i ) , 2 ) ) ; if ( i == 0 && j == 1 || maxLen < len ) { maxLen = len ; } } } System . out . println ( maxLen ) ; }
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