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)

(setq s(read-line))
(setq f 0)
(loop for i from 0 to (1-(length s))do
	  (loop for j from (1+ i)to(1-(length s))do
			(if(char=(char s i)(char s j))(incf f))))
(princ(if(> f 0)"no""yes"))