from collections import Counter

alpha = [chr(i) for i in range(ord('A'), ord('Z')+1)]
s = list(input().strip())
counter = Counter()
result = True

for c in s:
    if c not in alpha:
        result = False
        break
    if counter[c] == 1:
        result = False
        break
    counter[c] += 1

if result:
    print('YES')
else:
    print('NO')