#include <bits/stdc++.h>
using namespace std;
const int oo = 1e9 + 1;
const int mod = 1e9 + 7;
const int maxn = 1e5 + 5;
long long n, cnt[maxn], f[maxn];
map<long long, long long> mp;
string s;
void Init() {
  cin >> s;
  n = s.length();
  s.insert(0, " ");
  for (int i = 1; i <= n; ++i) {
    cnt[i] = cnt[i - 1];
    cnt[i] ^= (1LL << (s[i] - 'a'));
  }
}
void Solve() {
  mp[0] = 0;
  for (int i = 1; i <= n; ++i) {
    f[i] = i;
    if (mp.count(cnt[i])) f[i] = min(f[i], mp[cnt[i]] + 1);
    for (int j = 0; j < 26; ++j)
      if (((cnt[i] >> j) & 1) == 1) {
        int x = cnt[i] ^ (1LL << j);
        if (mp.count(x)) f[i] = min(f[i], mp[x] + 1);
      }
    if (!mp.count(cnt[i]))
      mp[cnt[i]] = f[i];
    else
      mp[cnt[i]] = min(mp[cnt[i]], f[i]);
  }
  cout << f[n];
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  Init();
  Solve();
}
