#include <bits/stdc++.h>
using namespace std;
const int MAXN = 200010;
const int MAXM = (1 << 26);
char s[MAXN];
int f[MAXM], g[MAXN];
int main() {
  scanf("%s", s + 1);
  int n = strlen(s + 1);
  for (int i = 1; i <= n; i++) {
    int c = s[i] - 'a';
    g[i] = g[i - 1] ^ (1 << c);
  }
  memset(f, 0x3f3f3f3f, sizeof(f));
  if (g[n] == 0) {
    cout << 1;
    return 0;
  }
  for (int i = 0; i < 26; i++) {
    f[(1 << i)] = 1;
    if (g[n] == (1 << i)) {
      cout << 1;
      return 0;
    }
  }
  f[0] = 0;
  for (int i = 2; i <= n; i++) {
    for (int j = 0; j < 26; j++) {
      int zt = g[i] ^ (1 << j);
      f[g[i]] = min(f[g[i]], f[zt] + 1);
    }
  }
  cout << f[g[n]];
  return 0;
}
