public static void main ( String [ ] args ) {
  FastReader in = new FastReader ( ) ;
  int n = in . nextInt ( ) ;
  long arr [ ] = new long [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    arr [ i ] = in . nextLong ( ) ;
  }
  HashMap < Long , Integer > hs = new HashMap < > ( ) ;
  int max = 1 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    for ( int j = i + 1 ;
    j < n ;
    j ++ ) {
      long s = arr [ i ] + arr [ j ] ;
      if ( hs . containsKey ( s ) ) {
        int get = hs . get ( s ) ;
        ++ get ;
        max = Math . max ( max , get ) ;
        hs . put ( s , get ) ;
      }
      else {
        hs . put ( s , 1 ) ;
      }
    }
  }
  System . out . println ( max ) ;
}

public static void main ( String [ ] args ) { FastReader in = new FastReader ( ) ; int n = in . nextInt ( ) ; long arr [ ] = new long [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { arr [ i ] = in . nextLong ( ) ; } HashMap < Long , Integer > hs = new HashMap < > ( ) ; int max = 1 ; for ( int i = 0 ; i < n ; i ++ ) { for ( int j = i + 1 ; j < n ; j ++ ) { long s = arr [ i ] + arr [ j ] ; if ( hs . containsKey ( s ) ) { int get = hs . get ( s ) ; ++ get ; max = Math . max ( max , get ) ; hs . put ( s , get ) ; } else { hs . put ( s , 1 ) ; } } } System . out . println ( max ) ; }
(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)))) (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) dimensions: (dimensions) value: (array_creation_expression type: (integral_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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier) (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))) (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: (identifier)) update: (update_expression (identifier)) body: (block (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: (identifier)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (array_access array: (identifier) index: (identifier))))) (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))) (expression_statement (update_expression (identifier))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (identifier))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (identifier))))) alternative: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (decimal_integer_literal)))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))