#include <bits/stdc++.h>
using namespace std;
map<int, int> ma;
int i, j, k, l, s, n, m, f[200005];
char c[200005];
inline int work(int x) {
  if (!x) return 0;
  int s = l + 1;
  if (ma[x]) s = f[ma[x]];
  for (int i = 0; i < 26; i++)
    if (ma[x ^ (1 << i)])
      s = min(s, f[ma[x ^ (1 << i)]]);
    else if (x == (1 << i))
      return 0;
  return s;
}
int main() {
  scanf("%s", c + 1);
  l = strlen(c + 1);
  s = 0;
  for (i = 1; i <= l; i++) {
    s ^= (1 << (c[i] - 97));
    f[i] = work(s) + 1;
    if (!ma[s] && s) ma[s] = i;
  }
  printf("%d\n", f[l]);
}
