S = input()
N = len(S)

def ctoi(c):
    return ord(c) - ord('a')

cums = [0]
for c in S:
    cums.append(cums[-1] ^ (1<<ctoi(c)))

dp = [N] * (N+1)
dp[0] = 1
idxs = {0:0}
for i,b in enumerate(cums):
    if b in idxs:
        dp[i] = dp[idxs[b]]
        continue
    idxs[b] = i
    dp[i] = dp[i-1] + 1
    cnt = 0
    for k in range(26):
        if b&(1<<k)==0: continue
        cnt += 1
        msk = b^(1<<k)
        if msk in idxs:
            dp[i] = min(dp[i], dp[idxs[msk]]+1)
    if cnt <= 1: dp[i] = 1
print(dp[-1])