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 Common Lisp (SBCL 1.1.14) (judge verdict: Accepted)

#-swank
(unless (member :child-sbcl *features*)
  (quit
	:unix-status
	(process-exit-code
	  (run-program *runtime-pathname*
				   `("--control-stack-size" "128MB"
					 "--noinform" "--disable-ldb" "--lose-on-corruption" "--end-runtime-options"
					 "--eval" "(push :child-sbcl *features*)"
					 "--script" ,(namestring *load-pathname*))
				   :output t :error t :input t))))

(let ((table (make-hash-table))
	  (ans t)
	  (s (concatenate 'list (read-line))))
  (mapc (lambda (x)
		  (if (gethash x table)
			(setf ans nil)
			(setf (gethash x table) t)))
		s)
  (princ (if ans
		   "yes"
		   "no")))