#include <bits/stdc++.h>
using namespace std;
int dp[202020];
map<int, int> dp2;
int main() {
  string s;
  cin >> s;
  int n = int(s.size());
  int x = 0;
  dp2[0] = 0;
  for (int i = 0; i < n; i++) {
    x ^= 1 << (s[i] - 'a');
    int m = 1e9;
    if (dp2.count(x) == 0) {
      dp2[x] = 1e9;
    }
    m = min(m, dp2[x]);
    for (int j = 0; j < 26; j++) {
      int xx = x ^ (1 << j);
      if (dp2.count(xx) == 0) dp2[xx] = 1e9;
      m = min(m, dp2[xx]);
    }
    dp2[x] = min(dp2[x], m + 1);
    dp[i] = m + 1;
  }
  cout << dp[n - 1] << endl;
}
