#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5;
map<int, bool> mp;
char s[maxn + 10];
int main() {
  scanf("%s", s);
  int n = strlen(s);
  int start = 0, pos = 0, ans = 0;
  mp[0] = true;
  int state = 1;
  for (int i = 1; i <= 26; i++) mp[state] = true, state <<= 1;
  while (start < n) {
    state = 0;
    for (int i = start; i < n; i++) {
      state ^= 1 << (s[i] - 'a');
      if (mp.find(state) != mp.end()) pos = i;
    }
    ans++, start = pos + 1;
  }
  printf("%d\n", ans);
  return 0;
}
