public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  int n = scan . nextInt ( ) ;
  int a = scan . nextInt ( ) ;
  int b = scan . nextInt ( ) ;
  int [ ] chores = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) chores [ i ] = scan . nextInt ( ) ;
  scan . close ( ) ;
  Arrays . sort ( chores ) ;
  if ( chores [ b - 1 ] == chores [ n - a ] ) System . out . println ( 0 ) ;
  else System . out . println ( chores [ n - a ] - chores [ b - 1 ] ) ;
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; int n = scan . nextInt ( ) ; int a = scan . nextInt ( ) ; int b = scan . nextInt ( ) ; int [ ] chores = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) chores [ i ] = scan . nextInt ( ) ; scan . close ( ) ; Arrays . sort ( chores ) ; if ( chores [ b - 1 ] == chores [ n - a ] ) System . out . println ( 0 ) ; else System . out . println ( chores [ n - a ] - chores [ b - 1 ] ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (identifier))))) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (decimal_integer_literal)))) alternative: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (identifier))) right: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))))))))))