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.