#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
const int inf = 0x3f3f3f3f;
char s[N];
int minn[1 << 26], pos[N], pre[N], dp[N], n;
int main() {
  scanf("%s", s + 1);
  n = strlen(s + 1);
  for (int i = 1; i <= n; ++i) {
    int f = s[i] - 'a';
    pre[i] = pre[i - 1] ^ (1 << f);
    dp[i] = dp[i - 1] + 1;
    if (minn[i] == 0) minn[i] = inf;
    dp[i] = min(dp[i], minn[i] + 1);
    for (int j = 0; j < 26; ++j) {
      int k = pre[i] ^ (1 << j);
      if (minn[k] == 0) minn[k] = inf;
      dp[i] = min(dp[i], minn[k] + 1);
    }
    minn[pre[i]] = min(dp[i], minn[pre[i]]);
  }
  printf("%d\n", dp[n]);
  return 0;
}
