#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
signed main() {
  string s;
  cin >> s;
  map<int, int> d;
  d[0] = 0;
  int m = 0;
  for (auto c : s) {
    m ^= (1 << (c - 'a'));
    if (!d.count(m)) {
      int res = 1e9;
      for (int i = 0; i < 26; ++i) {
        int from = m ^ (1 << i);
        if (d.count(from)) {
          res = min(res, d[from] + 1);
        }
      }
      assert(res != 1e9);
      d[m] = res;
    }
  }
  cout << max(1, d[m]) << '\n';
}
