#include <bits/stdc++.h>
using namespace std;
constexpr long long INF = 1e18;
template <class T>
inline bool CHMAX(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool CHMIN(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
signed main() {
  string s;
  cin >> s;
  map<vector<long long>, long long> mp;
  auto v = vector<long long>(26, 0);
  for (long long i = (0); i < (long long)(s.size()); i++) {
    v[s[i] - 'a'] ^= 1;
    mp[v] = i;
  }
  auto dp = vector<long long>(s.size() + 1, INF);
  dp[0] = 0;
  auto tmp = vector<long long>(26, 0);
  for (long long i = (0); i < (long long)(s.size()); i++) {
    CHMIN(dp[i + 1], dp[i] + 1);
    for (long long j = (0); j < (long long)(26); j++) {
      tmp[j] ^= 1;
      if (mp.count(tmp)) CHMIN(dp[mp[tmp] + 1], dp[i] + 1);
      tmp[j] ^= 1;
    }
    tmp[s[i] - 'a'] ^= 1;
  }
  if (*max_element(tmp.begin(), tmp.end()))
    cout << dp[s.size()] << endl;
  else
    cout << 1 << endl;
}
