#include <bits/stdc++.h>
using namespace std;
char s[200010];
int dp[1 << 26], q[200010], qs;
map<int, vector<int> > e;
bool can[1 << 26];
int main() {
  int l;
  scanf("%s", s);
  for (l = 0; s[l]; l++)
    ;
  int b = 0;
  can[0] = 1;
  for (int i = 0; i < l; i++) {
    int x = s[i] - 'a';
    b ^= 1 << x;
  }
  int tb = b;
  can[b] = 1;
  for (int i = 0; i < 1 << 26; i++) {
    dp[i] = -1;
  }
  for (int i = l - 1; i >= 0; i--) {
    int x = s[i] - 'a';
    b ^= 1 << x;
    can[b] = 1;
    for (int j = 0; j < 26; j++) {
      int y = b ^ (1 << j);
      if (can[y]) {
        e[b].push_back(y);
      }
    }
  }
  dp[0] = 0;
  qs++;
  int p = 0;
  while (p < qs) {
    int x = q[p++];
    vector<int> &to = e[x];
    for (int i = 0; i < to.size(); i++) {
      int y = to[i];
      if (dp[y] == -1) {
        dp[y] = dp[x] + 1;
        q[qs++] = y;
      }
    }
  }
  printf("%d\n", dp[tb] == 0 ? 1 : dp[tb]);
  return 0;
}
