#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 2e5;
int dp[1 + MAX_N];
char s[1 + MAX_N];
int bin[1 + MAX_N];
map<int, int> f;
const int SIGMA = 'z' - 'a' + 1;
int main() {
  cin >> (s + 1);
  int n = strlen(s + 1);
  for (int i = 1; i <= n; i++) bin[i] = (1 << (s[i] - 'a'));
  f[0] = 1;
  int sm = 0;
  for (int i = 1; i <= n; i++) {
    sm ^= bin[i];
    if (f[sm])
      dp[i] = dp[f[sm] - 1];
    else
      dp[i] = i;
    for (int j = 0; j < SIGMA; j++) {
      int smp = sm ^ (1 << j);
      if (f[smp]) dp[i] = min(dp[i], dp[f[smp] - 1]);
    }
    dp[i]++;
    if (!f[sm]) f[sm] = i + 1;
  }
  cout << dp[n];
  return 0;
}
