import string

ALPHABETS = string.ascii_lowercase

s = input()
N = len(s)
MAX = 2 * 10 ** 5
a = 0
dp = {}
dp[0] = 0
bits = [2 ** i for i in range(26)]

for c in s:
    a = a ^ bits[ALPHABETS.index(c)]
    dp[a] = min(dp.get(a, MAX), min([dp.get(a ^ 2 ** j, MAX) if not j == -1 else dp.get(a ^ 0, MAX) for j in range(-1, 26)]) + 1)

print(dp[a] if dp[a] != 0 else 1)
