from collections import Counter
from string import ascii_lowercase
from functools import lru_cache
import sys
s = input()
sys.setrecursionlimit(100000000)

@lru_cache(maxsize=-1)
def solve(S):
    if len(S)==1:
        return 1
    if len(S)==0:
        return 0
    tmp_c = Counter(S)
    if sum(tmp_c[s_tmp]%2 for s_tmp in ascii_lowercase)<=1:
        return 1
    #print(S)
    res = len(S)
    counter = Counter()
    for i,val_s in enumerate(S):
        counter[val_s]+=1
        if sum(counter[s_tmp]%2 for s_tmp in ascii_lowercase)<=1:
             res= min(res,1+ solve(S[i+1:]))

    return res


print(solve(s))