public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int num = Integer . parseInt ( sc . nextLine ( ) ) ;
  List < int [ ] > list = new ArrayList < > ( ) ;
  for ( int i = 0 ;
  i < num ;
  i ++ ) {
    String [ ] str = sc . nextLine ( ) . split ( " " ) ;
    list . add ( Stream . of ( str ) . mapToInt ( Integer :: parseInt ) . toArray ( ) ) ;
  }
  double maxLength = 0 ;
  for ( int i = 0 ;
  i < list . size ( ) ;
  i ++ ) {
    int [ ] baseNums = list . get ( i ) ;
    for ( int k = 0 ;
    k < list . size ( ) ;
    k ++ ) {
      if ( i <= k ) {
        continue ;
      }
      int [ ] targetNums = list . get ( k ) ;
      double xLength = Math . pow ( Math . abs ( baseNums [ 0 ] - targetNums [ 0 ] ) , 2 ) ;
      double yLength = Math . pow ( Math . abs ( baseNums [ 1 ] - targetNums [ 1 ] ) , 2 ) ;
      double sqrt = Math . sqrt ( xLength + yLength ) ;
      if ( sqrt > maxLength ) {
        maxLength = sqrt ;
      }
    }
  }
  System . out . println ( maxLength ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int num = Integer . parseInt ( sc . nextLine ( ) ) ; List < int [ ] > list = new ArrayList < > ( ) ; for ( int i = 0 ; i < num ; i ++ ) { String [ ] str = sc . nextLine ( ) . split ( " ▁ " ) ; list . add ( Stream . of ( str ) . mapToInt ( Integer :: parseInt ) . toArray ( ) ) ; } double maxLength = 0 ; for ( int i = 0 ; i < list . size ( ) ; i ++ ) { int [ ] baseNums = list . get ( i ) ; for ( int k = 0 ; k < list . size ( ) ; k ++ ) { if ( i <= k ) { continue ; } int [ ] targetNums = list . get ( k ) ; double xLength = Math . pow ( Math . abs ( baseNums [ 0 ] - targetNums [ 0 ] ) , 2 ) ; double yLength = Math . pow ( Math . abs ( baseNums [ 1 ] - targetNums [ 1 ] ) , 2 ) ; double sqrt = Math . sqrt ( xLength + yLength ) ; if ( sqrt > maxLength ) { maxLength = sqrt ; } } } System . out . println ( maxLength ) ; }
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