#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;

signed main() {
#ifdef LOCAL
  assert(freopen("d.in", "r", stdin));
#endif
  string s;
  cin >> s;
  map<int, int> d;
  d[0] = 0;
  int m = 0;
  for (auto c : s) {
    m ^= (1 << (c - 'a'));
    int res = 1e9;
    if (d.count(m))
      res = d[m];
    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';
}