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)


input = gets.chomp
split = input.split("")

answer = "yes"

count_letters = Array.new(27, true)

for letter in split do
	i = letter.encode( "UTF-8" ).ord - 96
	if count_letters[i]!=true
		answer = "no"
		break
	else
		count_letters[i] = false
	end
end

puts answer