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.chomp
v = [0] * 26

s.split('').each do |c|
  v[c.ord - 'a'.ord] += 1
end

flag = true
26.times do |i|
  if v[i] > 1 then
    flag = false
  end
end

puts (flag ? 'yes' : 'no')