#include <bits/stdc++.h>
using namespace std;
template <typename T>
using V = vector<T>;
template <typename T>
using VV = V<V<T>>;
template <typename T, typename U>
using P = pair<T, U>;
using ll = int64_t;
using PLL = P<ll, ll>;
template <typename T>
const T &var_min(const T &t) {
  return t;
}
template <typename T>
const T &var_max(const T &t) {
  return t;
}
template <typename Head, typename... Tail>
const Head &var_min(const Head &head, const Tail &...tail) {
  return min(head, var_min(tail...));
}
template <typename Head, typename... Tail>
const Head &var_max(const Head &head, const Tail &...tail) {
  return max(head, var_max(tail...));
}
template <typename T, typename... Tail>
void chmin(T &t, const Tail &...tail) {
  t = var_min(t, tail...);
}
template <typename T, typename... Tail>
void chmax(T &t, const Tail &...tail) {
  t = var_max(t, tail...);
}
string to_string(const string &s) { return s; }
template <typename T>
string to_string(const V<T> &v);
template <typename T, typename U>
string to_string(const P<T, U> &p) {
  string ret = "(";
  ret += to_string(p.first);
  ret += ", ";
  ret += to_string(p.second);
  ret += ")";
  return move(ret);
}
template <typename T>
string to_string(const V<T> &v) {
  string ret = "{";
  for (const T &t : v) {
    ret += to_string(t);
    ret += ", ";
  }
  ret += "}";
  return move(ret);
}
template <typename T>
void debug_func(const T &t, const string &s = "") {
  if (s.size()) cout << s << " = ";
  cout << to_string(t) << ((s).size() ? "\n" : "") << flush;
  ;
}
template <typename T>
void debug_func_mult(int idx, const V<string> &names, const T &t) {
  debug_func(t, names[idx]);
}
template <typename T>
void debug_func_mult(const V<string> &names, const T &t) {
  debug_func(t, names[0]);
}
template <typename Head, typename... Tail>
void debug_func_mult(int idx, const V<string> &names, const Head &head,
                     const Tail &...args) {
  debug_func(head, names[idx]);
  debug_func_mult(idx + 1, names, args...);
}
template <typename Head, typename... Tail>
void debug_func_mult(const V<string> &names, const Head &head,
                     const Tail &...args) {
  debug_func(head, names[0]);
  debug_func_mult(1, names, args...);
}
V<string> split_names(string &&s) {
  replace((s).begin(), (s).end(), ' ', ',');
  V<string> ret;
  istringstream ss(s);
  string t;
  while (getline(ss, t, ','))
    if (t.size()) ret.push_back(move(t));
  return move(ret);
}
void init_io() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(30);
}
const ll INF = 5e15;
map<ll, V<ll>> idxv;
V<ll> oev;
V<ll> memo(2e5 + 10, INF);
string S;
ll calc(ll idx) {
  if (memo[idx] != INF) return memo[idx];
  if (idx > S.size()) return 0;
  ll bs = oev[idx];
  ll ret = calc(max(idx + 1, idxv[bs].back())) + 1;
  for (ll i = 0; i < 26; i++) {
    ll nidx = bs ^ (1ll << i);
    const auto &v = idxv[nidx];
    if (v.size() == 0) continue;
    ll right = v.back();
    if (right < idx) continue;
    chmin(ret, calc(right) + 1);
  }
  return memo[idx] = ret;
}
int main() {
  init_io();
  cin >> S;
  ll now = 0;
  oev.push_back(0);
  idxv[0].push_back(0);
  for (ll i = 0; i < S.size(); i++) {
    now ^= (1ll << (S[i] - 'a'));
    oev.push_back(now);
    idxv[now].push_back(i + 1);
  }
  cout << calc(0) - 1 << '\n';
  return 0;
}
