#include <bits/stdc++.h>
template <typename T1, typename T2>
inline void chmin(T1 &a, T2 b) {
  if (a > b) a = b;
}
template <typename T1, typename T2>
inline void chmax(T1 &a, T2 b) {
  if (a < b) a = b;
}
using long long int = long long int;
using ull = long long unsigned int;
using Int = long long int;
using namespace std;
class Solve {
 public:
  void solve() {
    string S;
    cin >> S;
    Int sum = 0;
    Int N = S.size();
    vector<Int> dp(N + 1, (long long int)5e15);
    map<Int, Int> mp;
    dp[0] = 0;
    mp[0] = 0;
    for (int i = 0; i < N; ++i) {
      sum ^= (1ll << (S[i] - 'a'));
      chmin(dp[i + 1], dp[i] + 1);
      if (mp.count(sum)) {
        chmin(dp[i + 1], mp[sum]);
      }
      mp[sum] = dp[i + 1];
    }
    Int ans = max<Int>(dp[N], 1);
    cout << ans << endl;
  }
};
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  Solve().solve();
  return 0;
}
