#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int vis[26] = {0};
string s;
int dfs(int x) {
  if (x == s.size()) return 0;
  int index = 0;
  memset(vis, 0, sizeof(vis));
  for (int i = x; i < s.size(); i++) {
    vis[s[i] - 'a']++;
    int tot = 0;
    for (int j = 0; j < 26; j++) {
      if (vis[j] & 1) tot++;
    }
    if (tot < 2) index = i;
  }
  return 1 + dfs(index + 1);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> s;
  cout << dfs(0) << endl;
  return 0;
}
