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)

$str = gets
$sstr = $str.split("")

$count = 0
$last = $sstr.length - 2

for i in 0..$last
  for s in i+1..$last
    if $sstr[i] == $sstr[s]
      $count += 1
    end
  end
end

if $count > 0
  puts "no"
else puts "yes"
end