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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main( args : Array<String> ) {
  val xs = readLine()!!.toList()
  when {
    xs.size == xs.toSet().size -> "yes"
    else -> "no"
  }.let { println(it) }
}