public static void main ( String [ ] args ) {
  Scanner input = new Scanner ( System . in ) ;
  int n = input . nextInt ( ) ;
  input . nextLine ( ) ;
  String s = input . nextLine ( ) ;
  input . close ( ) ;
  int [ ] pre = new int [ n + 1 ] ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    if ( s . charAt ( i - 1 ) == '0' ) {
      pre [ i ] = pre [ i - 1 ] + 1 ;
    }
    else {
      pre [ i ] = pre [ i - 1 ] - 1 ;
    }
  }
  int [ ] mp = new int [ 2 * n + 1 ] ;
  mp [ 0 ] = 0 ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    if ( pre [ i ] < 0 ) {
      if ( mp [ n + pre [ i ] ] == 0 ) {
        mp [ n + pre [ i ] ] = i ;
      }
    }
    else if ( pre [ i ] > 0 ) {
      if ( mp [ pre [ i ] ] == 0 ) {
        mp [ pre [ i ] ] = i ;
      }
    }
  }
  int ans = 0 ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    if ( pre [ i ] < 0 ) {
      ans = Math . max ( ans , i - mp [ n + pre [ i ] ] ) ;
    }
    else {
      ans = Math . max ( ans , i - mp [ pre [ i ] ] ) ;
    }
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner input = new Scanner ( System . in ) ; int n = input . nextInt ( ) ; input . nextLine ( ) ; String s = input . nextLine ( ) ; input . close ( ) ; int [ ] pre = new int [ n + 1 ] ; for ( int i = 1 ; i <= n ; i ++ ) { if ( s . charAt ( i - 1 ) == '0' ) { pre [ i ] = pre [ i - 1 ] + 1 ; } else { pre [ i ] = pre [ i - 1 ] - 1 ; } } int [ ] mp = new int [ 2 * n + 1 ] ; mp [ 0 ] = 0 ; for ( int i = 1 ; i <= n ; i ++ ) { if ( pre [ i ] < 0 ) { if ( mp [ n + pre [ i ] ] == 0 ) { mp [ n + pre [ i ] ] = i ; } } else if ( pre [ i ] > 0 ) { if ( mp [ pre [ i ] ] == 0 ) { mp [ pre [ i ] ] = i ; } } } int ans = 0 ; for ( int i = 1 ; i <= n ; i ++ ) { if ( pre [ i ] < 0 ) { ans = Math . max ( ans , i - mp [ n + pre [ i ] ] ) ; } else { ans = Math . max ( ans , i - mp [ pre [ i ] ] ) ; } } 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)))) (expression_statement (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)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (binary_expression left: (identifier) right: (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 (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (decimal_integer_literal)))) right: (character_literal))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal))))) alternative: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)))))))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (identifier)) right: (decimal_integer_literal)))))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (decimal_integer_literal)) right: (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 (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))) right: (identifier)))))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (array_access array: (identifier) index: (identifier))) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (array_access array: (identifier) index: (identifier))) right: (identifier)))))))))) (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 (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (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: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))))))))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (identifier) right: (array_access array: (identifier) index: (array_access array: (identifier) index: (identifier)))))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))