public static void main ( String [ ] args ) throws IOException {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) , c = n / 2 ;
  System . out . println ( ++ c ) ;
  for ( int i = 1 ;
  i <= c ;
  i ++ ) System . out . println ( 1 + " " + i ) ;
  for ( int i = 2 ;
  i <= n - c + 1 ;
  i ++ ) System . out . println ( c + " " + i ) ;
}

public static void main ( String [ ] args ) throws IOException { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) , c = n / 2 ; System . out . println ( ++ c ) ; for ( int i = 1 ; i <= c ; i ++ ) System . out . println ( 1 + " ▁ " + i ) ; for ( int i = 2 ; i <= n - c + 1 ; i ++ ) System . out . println ( c + " ▁ " + i ) ; }
(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))) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (update_expression (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 (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (string_literal)) 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: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (identifier) right: (string_literal)) right: (identifier))))))))