Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

2 ≤ |S| ≤ 26, where |S| denotes the length of S.

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If all the characters in S are different, print yes (case-sensitive); otherwise, print no.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in OCaml (4.02.3) (judge verdict: Accepted)

open Batteries
open Printf
let () =
  let s = Scanf.scanf "%s " (fun a -> a) in
  let l = String.to_list s in
  let sl = List.sort_uniq compare l in

  Printf.printf "%s\n" @@
  if List.length l = (List.length sl) then "yes" else "no"