public static void main ( String [ ] args ) throws IOException {
  Scanner input = new Scanner ( System . in ) ;
  int n = input . nextInt ( ) ;
  int s = input . nextInt ( ) ;
  long total = s ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    total = Math . max ( total , input . nextInt ( ) + input . nextInt ( ) ) ;
  }
  System . out . println ( total ) ;
}

public static void main ( String [ ] args ) throws IOException { Scanner input = new Scanner ( System . in ) ; int n = input . nextInt ( ) ; int s = input . nextInt ( ) ; long total = s ; for ( int i = 1 ; i <= n ; i ++ ) { total = Math . max ( total , input . nextInt ( ) + input . nextInt ( ) ) ; } System . out . println ( total ) ; }
(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: (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: (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: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))