#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int N = 200000 + 10;
string s;
int n;
int val[N];
map<int, vector<int> > x;
int dp[N];
int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cin >> s;
  n = s.size();
  map<char, int> h;
  for (int i = 0; i < s.size(); i++) {
    h[s[i]]++;
    int temp = 0;
    for (int j = 0; j < 26; j++) {
      temp *= 2;
      temp += (h['a' + j] % 2);
    }
    val[i] = temp;
    x[temp].push_back(i);
  }
  int num = 0;
  for (auto it = h.begin(); it != h.end(); it++) {
    if ((*it).second % 2 == 1) {
      num++;
    }
  }
  if (num <= 1) {
    cout << 1 << endl;
    return 0;
  }
  dp[0] = 1;
  for (int i = 1; i < n; i++) {
    dp[i] = dp[i - 1] + 1;
    int temp = val[i], temp1;
    int ind = x[temp][0];
    dp[i] = min(dp[i], dp[ind] + 1);
    for (int j = 0; j < 26; j++) {
      temp1 = (temp ^ (1 << j));
      if (temp1 == 0) {
        dp[i] = 1;
      }
      if (x[temp1].size() > 0) {
        ind = x[temp1][0];
        if (ind < i) {
          dp[i] = min(dp[i], dp[ind] + 1);
        }
      }
    }
    if (temp == 0) {
      dp[i] = 1;
    }
  }
  cout << dp[n - 1] << endl;
  return 0;
}
