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 Perl (5.26.1) (judge verdict: Accepted)

$s1 = <>;
@s2 = split(//,$s1);
$h{$_}=1 for (@s2);
if (length($s1) == (scalar keys %h)) {
    print 'yes';
}
else {
    print 'no';
}