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
w = []
S.size.times do |x|
  w << S[x]
end
# p w
w.sort!
dup = false
(0..(S.size-2)).each do |x|
  if w[x] == w[x+1] then
    dup = true
    break
  end
end
if dup then
  puts 'no'
else
  puts 'yes'
end