public static void main ( String args [ ] ) {
  FastScanner input = new FastScanner ( ) ;
  int n = input . nextInt ( ) ;
  String s = input . next ( ) ;
  int left = 0 ;
  int right = n - 1 ;
  int zero = 0 ;
  int one = 0 ;
  long ans = 0 ;
  HashMap < Integer , Integer > map = new HashMap < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( s . charAt ( i ) == '0' ) zero ++ ;
    else one ++ ;
    if ( one - zero == 0 ) {
      ans = Math . max ( ans , i + 1 ) ;
    }
    else if ( map . containsKey ( one - zero ) ) {
      ans = Math . max ( ans , i - map . get ( one - zero ) ) ;
    }
    else map . put ( one - zero , i ) ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String args [ ] ) { FastScanner input = new FastScanner ( ) ; int n = input . nextInt ( ) ; String s = input . next ( ) ; int left = 0 ; int right = n - 1 ; int zero = 0 ; int one = 0 ; long ans = 0 ; HashMap < Integer , Integer > map = new HashMap < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( s . charAt ( i ) == '0' ) zero ++ ; else one ++ ; if ( one - zero == 0 ) { ans = Math . max ( ans , i + 1 ) ; } else if ( map . containsKey ( one - zero ) ) { ans = Math . max ( ans , i - map . get ( one - zero ) ) ; } else map . put ( one - zero , i ) ; } System . out . println ( ans ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier) dimensions: (dimensions))) 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: (type_identifier) 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: (integral_type) declarator: (variable_declarator name: (identifier) value: (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: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (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)))) (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 (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (expression_statement (update_expression (identifier))) alternative: (expression_statement (update_expression (identifier)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (identifier) right: (decimal_integer_literal))))))) alternative: (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier))))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier)))))))))) alternative: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier)) (identifier)))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))