#include <bits/stdc++.h>
using namespace std;
const int maxn = (1 << 26) + 100;
const int maxm = 2e5 + 100;
int g[maxn];
char s[maxm];
int dp[maxm];
int main() {
  ios::sync_with_stdio(0);
  cin >> (s + 1);
  fill(g, g + maxn, 100100);
  g[0] = 0;
  dp[0] = 1;
  int cd = 0, len = strlen(s + 1);
  for (int i = 1; i <= len; ++i) {
    dp[i] = 100100;
    int tmp = s[i] - 'a';
    cd ^= (1 << tmp);
    for (int j = 0; j < 26; ++j) {
      int p = (1 << j) ^ cd;
      dp[i] = min(g[p] + 1, dp[i]);
    }
    dp[i] = min(g[cd] + 1, dp[i]);
    g[cd] = min(g[cd], dp[i]);
  }
  cout << dp[len] << endl;
  return 0;
}
