public static void main ( String [ ] args ) {
  Scanner scn = new Scanner ( System . in ) ;
  int n = scn . nextInt ( ) ;
  int k = scn . nextInt ( ) ;
  boolean [ ] row = new boolean [ n ] ;
  boolean [ ] col = new boolean [ n ] ;
  for ( int i = 0 ;
  i < k ;
  i ++ ) {
    int val = scn . nextInt ( ) ;
    int val2 = scn . nextInt ( ) ;
    row [ val - 1 ] = true ;
    col [ val2 - 1 ] = true ;
  }
  long ans = 0 ;
  for ( int i = 1 ;
  i < n - 1 ;
  i ++ ) {
    if ( n % 2 == 1 && i == n / 2 ) {
      if ( ! row [ i ] || ! col [ i ] ) {
        ans ++ ;
      }
    }
    else if ( ! row [ i ] || ! col [ i ] ) {
      ans = ans + ( ( ! row [ i ] && ! col [ i ] ) ? 2 : 1 ) ;
    }
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner scn = new Scanner ( System . in ) ; int n = scn . nextInt ( ) ; int k = scn . nextInt ( ) ; boolean [ ] row = new boolean [ n ] ; boolean [ ] col = new boolean [ n ] ; for ( int i = 0 ; i < k ; i ++ ) { int val = scn . nextInt ( ) ; int val2 = scn . nextInt ( ) ; row [ val - 1 ] = true ; col [ val2 - 1 ] = true ; } long ans = 0 ; for ( int i = 1 ; i < n - 1 ; i ++ ) { if ( n % 2 == 1 && i == n / 2 ) { if ( ! row [ i ] || ! col [ i ] ) { ans ++ ; } } else if ( ! row [ i ] || ! col [ i ] ) { ans = ans + ( ( ! row [ i ] && ! col [ i ] ) ? 2 : 1 ) ; } } System . out . println ( ans ) ; }
(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: (boolean_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (boolean_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (array_type element: (boolean_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (boolean_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 (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)))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (true))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (true))))) (local_variable_declaration type: (integral_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: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)) right: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal))))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (unary_expression operand: (array_access array: (identifier) index: (identifier))) right: (unary_expression operand: (array_access array: (identifier) index: (identifier))))) consequence: (block (expression_statement (update_expression (identifier)))))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (unary_expression operand: (array_access array: (identifier) index: (identifier))) right: (unary_expression operand: (array_access array: (identifier) index: (identifier))))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (parenthesized_expression (ternary_expression condition: (parenthesized_expression (binary_expression left: (unary_expression operand: (array_access array: (identifier) index: (identifier))) right: (unary_expression operand: (array_access array: (identifier) index: (identifier))))) consequence: (decimal_integer_literal) alternative: (decimal_integer_literal))))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))