#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  const int n = s.size();
  int hoge = 0;
  for (char c : s) hoge ^= 1 << c - 'a';
  if (hoge == 0) {
    cout << 1 << endl;
    return 0;
  }
  vector<int> x(n + 1);
  for (int i = 0; i < n; i++) {
    x[i + 1] = x[i] ^ (1 << s[i] - 'a');
  }
  map<int, vector<int>> mp;
  for (int i = 1; i <= n; i++) {
    mp[x[i]].push_back(i);
  }
  queue<int> q;
  q.push(0);
  vector<int> d(n + 1, 1e9);
  d[0] = 0;
  vector<int> cnt(n + 1, 10);
  while (!q.empty()) {
    int i = q.front();
    q.pop();
    for (int k = 0; k < 26; k++) {
      int y = x[i] ^ (1 << k);
      if (mp.count(y)) {
        auto &vec = mp[y];
        int j = vec.back();
        if (d[j] <= d[i] + 1) continue;
        d[j] = d[i] + 1;
        cnt[j]--;
        if (cnt[j] == 0) {
          vec.pop_back();
        }
        if (vec.empty()) {
          mp.erase(y);
        }
        q.push(j);
      }
    }
  }
  cout << d[n] << endl;
}
