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.

Examples

Input

uncopyrightable

Output

yes

Input

different

Output

no

Input

no

Output

yes

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