public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int k = sc . nextInt ( ) ;
  double [ ] w = new double [ n ] ;
  double [ ] p = new double [ n ] ;
  double pmax = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    w [ i ] = sc . nextDouble ( ) ;
    p [ i ] = sc . nextDouble ( ) ;
    pmax = Math . max ( pmax , p [ i ] ) ;
  }
  double low = 0 ;
  double upp = pmax ;
  double x = ( low + upp ) / 2 ;
  while ( upp - low > 0.00000001 ) {
    double [ ] c = new double [ n ] ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      c [ i ] = w [ i ] * ( p [ i ] - x ) ;
    }
    Arrays . sort ( c ) ;
    double sum = 0 ;
    for ( int i = n - 1 ;
    i >= n - k ;
    i -- ) {
      sum += c [ i ] ;
    }
    if ( sum > 0 ) {
      low = x ;
      x = ( low + upp ) / 2 ;
    }
    else {
      upp = x ;
      x = ( low + upp ) / 2 ;
    }
  }
  System . out . println ( x ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int k = sc . nextInt ( ) ; double [ ] w = new double [ n ] ; double [ ] p = new double [ n ] ; double pmax = 0 ; for ( int i = 0 ; i < n ; i ++ ) { w [ i ] = sc . nextDouble ( ) ; p [ i ] = sc . nextDouble ( ) ; pmax = Math . max ( pmax , p [ i ] ) ; } double low = 0 ; double upp = pmax ; double x = ( low + upp ) / 2 ; while ( upp - low > 0.00000001 ) { double [ ] c = new double [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { c [ i ] = w [ i ] * ( p [ i ] - x ) ; } Arrays . sort ( c ) ; double sum = 0 ; for ( int i = n - 1 ; i >= n - k ; i -- ) { sum += c [ i ] ; } if ( sum > 0 ) { low = x ; x = ( low + upp ) / 2 ; } else { upp = x ; x = ( low + upp ) / 2 ; } } System . out . println ( x ) ; }
(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: (array_type element: (floating_point_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (floating_point_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (array_type element: (floating_point_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (floating_point_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (floating_point_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (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: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (array_access array: (identifier) index: (identifier)))))))) (local_variable_declaration type: (floating_point_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (floating_point_type) declarator: (variable_declarator name: (identifier) value: (identifier))) (local_variable_declaration type: (floating_point_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) right: (decimal_integer_literal)))) (while_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_floating_point_literal))) body: (block (local_variable_declaration type: (array_type element: (floating_point_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (floating_point_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: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier)))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (local_variable_declaration type: (floating_point_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (decimal_integer_literal)))) condition: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) right: (decimal_integer_literal))))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) right: (decimal_integer_literal)))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))