Problem Statement

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

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.

Constraints

• 2 ≤ |S| ≤ 26, where |S| denotes the length of S.
• S consists of lowercase English letters.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

见题面 Input 部分

见题面 Output 部分