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