#include <bits/stdc++.h>
using namespace std;
const long long md = 1e9 + 7;
int freq[200005], n, dp[200005];
unordered_map<int, int> best;
int get(int k, int i) {
  return best.find(k) != best.end() ? dp[best[k]] : dp[i - 1];
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long q, m, k, h, ans = 0, sum = 0, p, x, y;
  string s;
  cin >> s;
  n = s.size();
  s = '.' + s;
  for (int i = 1; i <= n; ++i) freq[i] = freq[i - 1] ^ (1 << (s[i] - 'a'));
  best[0] = dp[0] = 0;
  for (int i = 1; i <= n; ++i) {
    dp[i] = 1 + get(freq[i], i);
    for (int j = 0; j < 26; ++j)
      dp[i] = min(dp[i], 1 + get(freq[i] ^ (1 << j), i));
    if (best.find(freq[i]) == best.end()) best[freq[i]] = i;
  }
  cout << dp[n];
}
