public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  PrintWriter pw = new PrintWriter ( System . out ) ;
  int n = sc . nextInt ( ) ;
  String s = sc . next ( ) ;
  int c = 1 ;
  int i = 0 ;
  String result = "" ;
  while ( i < s . length ( ) ) {
    result = result + s . charAt ( i ) ;
    i = i + c ;
    c ++ ;
  }
  System . out . println ( result ) ;
  pw . flush ( ) ;
  pw . close ( ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; PrintWriter pw = new PrintWriter ( System . out ) ; int n = sc . nextInt ( ) ; String s = sc . next ( ) ; int c = 1 ; int i = 0 ; String result = " " ; while ( i < s . length ( ) ) { result = result + s . charAt ( i ) ; i = i + c ; c ++ ; } System . out . println ( result ) ; pw . flush ( ) ; pw . close ( ) ; }
(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: (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: (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: (decimal_integer_literal))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (string_literal))) (while_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) body: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier)))) (expression_statement (update_expression (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))