#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T>
inline T sign(T x) {
  return T(x > 0) - T(x < 0);
}
template <typename T, typename S>
inline ostream& operator<<(ostream& os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const vector<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T>
inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto& elem : ret) cin >> elem;
  return ret;
}
const int MAXN = (int)2e5 + 77;
const int A = 26;
int dp[MAXN], a[MAXN], n;
map<int, int> mn;
void relax(int& x, int y) { x = (y < x ? y : x); }
int get_mn(int x) { return (mn.count(x) ? mn[x] : INT_INF); }
void solve() {
  auto line = fetch<string>();
  n = ((int)(line).size());
  for (int i = 1; i <= n; ++i) {
    int code = line[i - 1] - 'a';
    a[i] = 1 << code;
    a[i] ^= a[i - 1];
  }
  dp[0] = 0;
  mn[a[0]] = 0;
  for (int i = 1; i <= n; ++i) {
    dp[i] = INT_INF;
    relax(dp[i], get_mn(a[i]) + 1);
    ;
    ;
    for (int code = 0; code < A; ++code) {
      int b = a[i] ^ (1 << code);
      relax(dp[i], get_mn(b) + 1);
      ;
      ;
    }
    mn[a[i]] = min(get_mn(a[i]), dp[i]);
  }
  cout << dp[n] << '\n';
}
int main() {
  fast_io();
  solve();
  return 0;
}
