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)


def resolve():
    import sys
    input = sys.stdin.readline
    # row = [int(x) for x in input().rstrip().split(" ")]
    # n = int(input().rstrip())
    s = input().rstrip()
    chars = set()
    for c in s:
        if c in chars:
            print("no")
            return
        else:
            chars.add(c)

    print("yes")




if __name__ == "__main__":
    resolve()