#include <bits/stdc++.h>
using namespace std;
int a[200003];
int dp[(1 << 26) + 3];
int main() {
  string s;
  cin >> s;
  a[0] = (1 << (s[0] - 'a'));
  for (int i = 1; i < (int)s.length(); i++) {
    a[i] = 1 << (s[i] - 'a');
    a[i] ^= a[i - 1];
  }
  for (int i = 0; i < (1 << 26) + 1; i++) dp[i] = 1e9;
  dp[0] = 1;
  for (int i = 0; i < 26; i++) dp[1 << i] = 1;
  for (int i = 0; i < (int)s.length(); i++) {
    int t = 1 + dp[a[i]];
    for (int j = 0; j < 26; j++) {
      t = min(t, 1 + dp[(1 << j) ^ a[i]]);
    }
    dp[a[i]] = min(dp[a[i]], t);
  }
  cout << dp[a[(int)s.length() - 1]] << endl;
  return 0;
}
