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 Python (3.4.3) (judge verdict: Accepted)

s = input()
frag = 0
for i in range(len(s)):
    for j in range(len(s)-i-1):
        if s[i] == s[j+i+1]:
            frag += 1
            break
            
if frag == 0:
    print("yes")
else:
    print("no")