#include <bits/stdc++.h>
using namespace std;
const long long INF = 1001001001;
const long long LINF = 1001001001001001001;
const long long D4[] = {0, 1, 0, -1, 0};
const long long D8[] = {0, 1, 1, 0, -1, -1, 1, -1, 0};
template <class T>
bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
using pq = priority_queue<T, vector<T>, greater<T>>;
string s;
void solve();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cin >> s;
  solve();
}
void solve() {
  long long bit = 0;
  long long n = s.size();
  vector<long long> dp(n + 1, INF);
  dp[0] = 0;
  map<long long, long long> mp;
  mp.emplace(0, 0);
  for (long long i = 0; i < (n); ++i) {
    bit ^= 1 << (s[i] - 'a');
    for (long long j = 0; j < (26); ++j) {
      long long tmp = bit ^ (1 << j);
      if (mp.count(tmp)) chmin(dp[i + 1], dp[mp[tmp]] + 1);
    }
    if (!mp.count(bit)) mp[bit] = i + 1;
  }
  if (__builtin_popcount(bit) <= 1)
    cout << 1 << endl;
  else
    cout << dp[n] << endl;
}
