import string

ALPHABETS = string.ascii_lowercase
ALPHABETS_TO_INT = {}

for pos, c in enumerate(ALPHABETS):
    ALPHABETS_TO_INT[c] = pos
count = 1


def check(s):
    global count
    if is_available(s):
        return
    for i in range(1, len(s)):
        if is_available(s[i:]):
            count += 1
            # print(s[:i])
            check(s[:i])
            return
        elif is_available(s[:len(s)-i]):
            count += 1
            # print(s[len(s)-i:])
            check(s[len(s)-i:])
            return


def is_available(s):
    num_arr = [False] * 26
    for c in s:
        num_arr[ALPHABETS_TO_INT[c]] = not num_arr[ALPHABETS_TO_INT[c]]
    if num_arr.count(True) <= 1:
        return True
    return False


s = input()
check(s)
print(count)
