#include <bits/stdc++.h>
using namespace std;
const int N = 200005;
char s[N];
int n, sum[(1 << 26)], f[N];
int main() {
  scanf("%s", s + 1);
  n = strlen(s + 1);
  for (int i = 1; i <= n; i++) sum[i] = sum[i - 1] ^ (1 << (s[i] - 'a'));
  memset(f, 0x3f, sizeof(f));
  f[0] = 0;
  for (int i = 1; i <= n; i++) {
    f[sum[i]] = f[sum[i]] + 1;
    for (int j = 0; j < 26; j++)
      f[sum[i]] = min(f[sum[i]], f[sum[i] ^ (1 << j)] + 1);
  }
  printf("%d\n", max(f[sum[n]], 1));
  return 0;
}
