#include <bits/stdc++.h>
using namespace std;
char s[200005];
int n, tot, num[305], f[200005], sum[200005];
map<int, int> mp;
int main() {
  scanf("%s", s + 2);
  n = strlen(s + 2);
  mp[0] = 1;
  for (int i = 2; i <= n + 1; i++) {
    num[s[i]] ^= 1;
    if (num[s[i]])
      sum[i] = sum[i - 1] + (1 << (s[i] - 'a'));
    else
      sum[i] = sum[i - 1] - (1 << (s[i] - 'a'));
    f[i] = f[i - 1] + 1;
    if (mp[sum[i]]) f[i] = f[mp[sum[i]]];
    if (!mp[sum[i]]) mp[sum[i]] = i;
  }
  if (sum[n + 1] == n) {
    puts("1");
    return 0;
  }
  printf("%d\n", f[n + 1]);
  return 0;
}
