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 Ruby (2.3.3) (judge verdict: Wrong Answer)

str = gets.chomp

ary = {}

str.each_char{|c| if ary[c].nil? then ary[c] = 1 else ary[c] += 1 end}

r = false
ary.each{|a|r = true if a[1] > 1}
if r then 'yes' else 'no' end