#include <bits/stdc++.h>
using namespace std;
string s;
unordered_map<int, int> M;
int main() {
  ios::sync_with_stdio(false);
  cin >> s;
  int stat = 0;
  int l = s.length();
  M[0] = 0;
  for (int i = 0; i < l; i++) {
    stat ^= (1 << (s[i] - 'a'));
    int mi = 123456789;
    auto k = M.find(stat);
    if (k != M.end()) continue;
    for (int j = 0; j < 26; j++) {
      k = M.find(stat ^ (1 << j));
      if (k != M.end()) mi = min(mi, k->second);
    }
    M[stat] = mi + 1;
  }
  if (!stat)
    cout << 1 << endl;
  else
    cout << M[stat] << endl;
  return 0;
}
