import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import numpy as np

S = np.array(list(read().rstrip()),np.int32)

Scum = np.bitwise_xor.accumulate(1<<(S-97)).tolist()

bit = 1<<np.arange(26)

INF = 10**9
dp = np.full(1<<26,INF,np.int32)
dp[0] = 0

for cum in Scum:
    x = dp[cum^bit].min() + 1
    if dp[cum] > x:
        dp[cum] = x

answer = max(1,dp[cum])
print(answer)