#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void upd1(T& a, T b) {
  a > b ? a = b : 0;
}
template <class T>
inline void upd2(T& a, T b) {
  a < b ? a = b : 0;
}
struct ano {
  operator long long() {
    long long x = 0, y = 0, c = getchar();
    while (c < 48) y = c == 45, c = getchar();
    while (c > 47) x = x * 10 + c - 48, c = getchar();
    return y ? -x : x;
  }
} buf;
const int N = 2e5 + 5;
char a[N];
int b[N];
bitset<1 << 26> g;
map<int, int> f;
int main() {
  scanf("%s", a + 1);
  int n = strlen(a + 1);
  g[0] = 1;
  for (int i = 1; i <= n; ++i) {
    b[i] = b[i - 1] ^ 1 << a[i] - 97;
    if (!g[b[i]]) {
      g[b[i]] = 1;
      f[b[i]] = n;
      for (int j = 0; j < 26; ++j)
        if (g[b[i] ^ 1 << j]) upd1(f[b[i]], f[b[i] ^ 1 << j] + 1);
    }
  }
  printf("%d\n", b[n] ? f[b[n]] : 1);
}
