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
s_list = s.split("")
is_overlap = false

s_list.each{|item|
  count = s_list.count(item)
  if count > 1
    is_overlap = true
    break
  end
}
if is_overlap
  print "no\n"
else
  print "yes\n"
end