#include <bits/stdc++.h>
using namespace std;
long long a[200005];
long long dp[1 << 26];
long long ans[200005];
const long long INF = 1e17;
int main() {
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    a[i + 1] = (1ll << (s[i] - 'a')) ^ a[i];
  }
  for (int i = 0; i < (1 << 26); i++) dp[i] = INF;
  dp[0] = 0;
  long long tmp;
  for (int i = 1; i <= s.size(); i++) {
    tmp = dp[a[i]];
    for (int j = 0; j < 26; j++) {
      long long s = (1ll << j);
      tmp = min(tmp, dp[a[i] ^ s]);
    }
    dp[a[i]] = min(dp[a[i]], tmp + 1);
  }
  cout << tmp + 1 << endl;
}
