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 (7.3.0) (judge verdict: Accepted)

a = input()
alp =[0 for i in range(0 , 29)]
for i in a:
	alp[ord(i)-ord('a')]+=1
for i in range(0 , 26):
	if alp[i]>1:
		print("no")
		exit()
print("yes")
exit()