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: Wrong Answer)

s = list(input())
size = len(s)
count = 0 
ans = {}
for i in s:
    
    if i in ans.keys() :
        count += 1
    else : 
        ans[i] = 1
        pass
if count == 0 : print("YES")
else: print("NO")