public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  String s = sc . next ( ) ;
  if ( s . length ( ) == 1 ) {
    System . out . println ( s ) ;
    System . exit ( 0 ) ;
  }
  StringBuilder ans = new StringBuilder ( ) ;
  int i = s . length ( ) - 1 , j = 0 ;
  if ( ( s . length ( ) & 1 ) == 0 ) {
    for ( int l = 0 ;
    l < s . length ( ) / 2 ;
    l ++ ) {
      if ( i == j ) {
        ans . append ( s . charAt ( i ) ) ;
        break ;
      }
      ans . append ( s . charAt ( i ) ) ;
      i -- ;
      ans . append ( s . charAt ( j ) ) ;
      j ++ ;
    }
    System . out . println ( ans . reverse ( ) ) ;
  }
  else {
    int mid = s . length ( ) / 2 ;
    int x = mid , y = mid ;
    System . out . print ( s . charAt ( mid ) ) ;
    for ( int l = 0 ;
    l < mid ;
    l ++ ) {
      x ++ ;
      System . out . print ( s . charAt ( x ) ) ;
      y -- ;
      System . out . print ( s . charAt ( y ) ) ;
    }
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; String s = sc . next ( ) ; if ( s . length ( ) == 1 ) { System . out . println ( s ) ; System . exit ( 0 ) ; } StringBuilder ans = new StringBuilder ( ) ; int i = s . length ( ) - 1 , j = 0 ; if ( ( s . length ( ) & 1 ) == 0 ) { for ( int l = 0 ; l < s . length ( ) / 2 ; l ++ ) { if ( i == j ) { ans . append ( s . charAt ( i ) ) ; break ; } ans . append ( s . charAt ( i ) ) ; i -- ; ans . append ( s . charAt ( j ) ) ; j ++ ; } System . out . println ( ans . reverse ( ) ) ; } else { int mid = s . length ( ) / 2 ; int x = mid , y = mid ; System . out . print ( s . charAt ( mid ) ) ; for ( int l = 0 ; l < mid ; l ++ ) { x ++ ; System . out . print ( s . charAt ( x ) ) ; y -- ; System . out . print ( s . charAt ( y ) ) ; } } }
(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: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) consequence: (block (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 (decimal_integer_literal)))))) (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: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (if_statement condition: (parenthesized_expression (binary_expression left: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) right: (decimal_integer_literal))) consequence: (block (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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (break_statement))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (expression_statement (update_expression (identifier))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (expression_statement (update_expression (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) alternative: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (identifier)) declarator: (variable_declarator name: (identifier) value: (identifier))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (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 (update_expression (identifier))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (expression_statement (update_expression (identifier))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))))))))))