#include <bits/stdc++.h>
using namespace std;
const long long N = 2e5 + 5, inf = 1e13;
long long dp[N], prfx[N], best[1ll << 26];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  s = "$" + s;
  long long n = s.size();
  for (long long i = 1; i <= n; i++)
    prfx[i] = prfx[i - 1] ^ (1ll << (s[i] - 'a'));
  for (long long i = 0; i < (1ll << 26); i++) best[i] = inf;
  for (long long i = n; i >= 1; i--) {
    best[prfx[i]] = min(best[prfx[i]], dp[i + 1]);
    long long ans = best[prfx[i - 1]];
    for (long long j = 0; j < 26; j++)
      ans = min(ans, best[prfx[i - 1] ^ (1ll << j)]);
    dp[i] = ans + 1;
  }
  cout << dp[1];
}
