You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

print('Input a string: ')
s = input()
c = 0

#check for constraints
if 2<=len(s) and len(s) <= 26:
    s2 = ''.join(sorted(s))
 #   print(s2)

    for i in s2:
        if c > len(s):
            quit()
        if s2[c] == s2[c+1]:
            print('no')  # string is not unique
            quit()
        elif s2[c] != s2[c+1]:
            continue
print('yes') # string is unique


s = input()
c = 0

if len(s) < 2 or len(s) > 26:
    quit()
if len(s) >= 2 and len(s) <= 26:
    s2 = ''.join(sorted(s))
    for i in s2:
        if c+1 >= len(s):
            break
        elif s2[c] == s2[c+1]:
             print('no')
             quit()
        else:
            c = c + 1
print('yes')