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: Accepted)

S = gets.split("").sort

ans = "yes"

0.upto(S.length - 1) do |i| # 要素がある分だけ繰り返したいとき
  if S[i] == S[i + 1]
    ans  = "no"
  end
end

puts ans
# https://qiita.com/you8/items/1d25a63a67c10dada128