import string

ALPHABETS = string.ascii_lowercase

s = input()
N = len(s)
MAX = 2 * 10 ** 5
a = [0] * (N + 1)
for i, c in enumerate(s):
    idx = ALPHABETS.index(c)
    a[i+1] = a[i] ^ (2 ** idx)

opt = [0] * (N + 1)
dp = {}
dp[0] = 0
for i in range(1, N + 1):
    dp[a[i]] = min(dp.get(a[i], MAX), min([dp.get(a[i] ^ 2 ** j, MAX) if not j == -1 else dp.get(a[i] ^ 0, MAX) for j in range(-1, 26)]) + 1)

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