open Printf
open Scanf

let () =
        let s = read_line() in
        let rec iter i ans =
                if i = (String.length s) then
                        printf "%s\n" ans
                else if (i mod 2 = 0) then
                        iter (i + 1) (ans ^ (String.make 1 s.[i]))
                else
                        iter (i + 1) ans
        in iter 0 ""
