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 PyPy3 (2.4.0) (judge verdict: Accepted)

w = str(input())
W = sorted(w)

for i in range(len(W)-1):
  if W[i] != W[i+1]:
    f = True
  else:
    f = False
    break
print('yes' if f else 'no')