#include <bits/stdc++.h>
int main() {
  std::ios::sync_with_stdio(0);
  std::string s;
  std::cin >> s;
  int n = s.size();
  int st = 0;
  std::map<int, int> mp;
  mp[0] = 0;
  for (int i = 0; i < n; ++i) {
    st ^= (1 << (s[i] - 'a'));
    if (mp.count(st)) continue;
    int &ans = mp[st];
    ans = n + 1;
    for (int j = 0; j < 26; ++j) {
      int prev = st ^ (1 << j);
      if (mp.count(prev)) {
        ans = std::min(ans, mp[prev] + 1);
      }
    }
  }
  int ans = mp[st];
  if (ans == 0) ans = 1;
  std::cout << ans << std::endl;
  return 0;
}
