Zebra - also a horse

A string s is defined as a zebra if it can be divided into several substrings s = x[1]+x[2]+...+x[k] (k ≥ 1) such that the following conditions hold:

• Each substring x[i] consists of identical characters;

• No two substrings x[i] and x[j] (i ≠ j) share the same character.

For instance, the string "aaabbccc" qualifies as a zebra, whereas the string "aabbbaa" does not.

You are provided with a string. Determine if it is a zebra.

Input

The first line contains the string s (1 ≤ |s| ≤ 10^5). The string consists solely of lowercase Latin letters.

Output

Print "YES" if the string is a zebra, or "NO" if it is not.

Examples