#include <bits/stdc++.h>
using namespace std;
const int maxn = (int)(2e5) + 5;
map<int, int> now;
int f[maxn];
char s[maxn];
int main() {
  scanf("%s", s + 1);
  int n = strlen(s + 1), w = 0;
  memset(f, 0x3f, sizeof(f));
  now[0] = 0;
  f[0] = 0;
  for (int i = 1; i <= n; ++i) {
    w ^= (1 << (s[i] - 26));
    if (now.count(w)) {
      int l = now[w];
      f[i] = min(f[i], f[i - 1] + 1);
      f[i] = min(f[i], f[l] + 1);
      if (l > 0) f[i] = min(f[i], f[l - 1] + 1);
      if (i < n) f[i + 1] = min(f[i], f[l]) + 1;
    } else
      now[w] = i, f[i] = min(f[i], f[i - 1] + 1);
  }
  return printf("%d\n", f[n]), 0;
}
