#include <bits/stdc++.h>
using namespace std;
string s;
int d[200001];
map<int, int> best;
int main() {
  cin >> s;
  int n = s.size(), x = 0;
  s = ' ' + s;
  best[0] = 0;
  for (int i = 1; i <= n; i++) {
    d[i] = i;
    x ^= 1 << (s[i] - 'a');
    for (int j = 0; j < 26; j++)
      if (best.count(x ^ (1 << j))) d[i] = min(d[i], best[x ^ (1 << j)] + 1);
    if (best.count(x))
      d[i] = min(d[i], best[x]);
    else
      best[x] = d[i];
  }
  cout << max(1, d[n]) << endl;
  return 0;
}
