#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
template <class T = int>
using V = vector<T>;
template <class T = int>
using VV = V<V<T> >;
template <class T>
void assign(V<T>& v, int n, const T& a = T()) {
  v.assign(n, a);
}
template <class T, class... Args>
void assign(V<T>& v, int n, const Args&... args) {
  v.resize(n);
  for (auto&& e : v) assign(e, args...);
}
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  string s;
  cin >> s;
  int n = s.size();
  map<int, int> mp;
  int x = 0;
  mp[x] = 0;
  V<> dp(n + 1);
  for (int i = 0; i < n; ++i) {
    x ^= 1 << s[i] - 'a';
    if (mp.count(x))
      dp[i + 1] = dp[mp[x]];
    else
      dp[i + 1] = dp[i] + 1;
    mp[x] = i + 1;
  }
  cout << max(dp[n], 1) << '\n';
}
