public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  PrintWriter pw = new PrintWriter ( System . out ) ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  int temp = 1 ;
  int [ ] a = sc . nextArr ( n * 2 ) ;
  int c = 0 ;
  int j = 0 ;
  int [ ] arr = new int [ 100 ] ;
  boolean flag = false ;
  while ( temp <= m ) {
    for ( int i = 0 ;
    i < a . length - 1 ;
    i = i + 2 ) {
      if ( temp >= a [ i ] && temp <= a [ i + 1 ] ) {
        c ++ ;
        flag = true ;
        break ;
      }
      else {
        flag = false ;
      }
    }
    if ( ! flag ) {
      arr [ j ] = temp ;
      j ++ ;
    }
    temp ++ ;
  }
  System . out . println ( m - c ) ;
  for ( int i = 0 ;
  i < j ;
  i ++ ) {
    System . out . print ( arr [ i ] + " " ) ;
  }
  pw . flush ( ) ;
  pw . close ( ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; PrintWriter pw = new PrintWriter ( System . out ) ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; int temp = 1 ; int [ ] a = sc . nextArr ( n * 2 ) ; int c = 0 ; int j = 0 ; int [ ] arr = new int [ 100 ] ; boolean flag = false ; while ( temp <= m ) { for ( int i = 0 ; i < a . length - 1 ; i = i + 2 ) { if ( temp >= a [ i ] && temp <= a [ i + 1 ] ) { c ++ ; flag = true ; break ; } else { flag = false ; } } if ( ! flag ) { arr [ j ] = temp ; j ++ ; } temp ++ ; } System . out . println ( m - c ) ; for ( int i = 0 ; i < j ; i ++ ) { System . out . print ( arr [ i ] + " ▁ " ) ; } pw . flush ( ) ; pw . close ( ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_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: (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: (decimal_integer_literal))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (decimal_integer_literal)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (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 (decimal_integer_literal))))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (false))) (while_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) body: (block (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (field_access object: (identifier) field: (identifier)) right: (decimal_integer_literal))) update: (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal))) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier))) right: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal)))))) consequence: (block (expression_statement (update_expression (identifier))) (expression_statement (assignment_expression left: (identifier) right: (true))) (break_statement)) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (false))))))) (if_statement condition: (parenthesized_expression (unary_expression operand: (identifier))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier))) (expression_statement (update_expression (identifier))))) (expression_statement (update_expression (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (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 (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (string_literal))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))