#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n = s.size();
  set<pair<int, int> > st;
  st.insert(pair<int, int>(0, 0));
  int dp[200001];
  int a[200001];
  dp[0] = 0;
  a[0] = 0;
  for (int i = 1; i <= n; i++) {
    a[i] = a[i - 1] ^ (1 << (s[i - 1] - 'a'));
    if (a[i] == 0) {
      dp[i] = 1;
      st.insert(pair<int, int>(a[i], i));
      continue;
    }
    dp[i] = dp[i - 1] + 1;
    for (int j = 0; j < 26; j++) {
      int a0 = a[i] ^ (1 << j);
      auto itr = st.upper_bound(pair<int, int>(a0, 1e9));
      itr--;
      if ((*itr).first == a0) {
        int i0 = (*itr).second;
        dp[i] = min(dp[i], dp[i0] + 1);
      }
    }
    st.insert(pair<int, int>(a[i], i));
  }
  cout << dp[n] << endl;
  return 0;
}
