#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <functional>
#include <set>
#include <ctime>
#include <random>
#include <chrono>
#include <cassert>
#include <tuple>
#include <utility>
using namespace std;

namespace {
  using Integer = long long; //__int128;
  template<class T, class S> istream& operator >> (istream& is, pair<T,S>& p){return is >> p.first >> p.second;}
  template<class T> istream& operator >> (istream& is, vector<T>& vec){for(T& val: vec) is >> val; return is;}
  template<class T> istream& operator ,  (istream& is, T& val){ return is >> val;}
  template<class T, class S> ostream& operator << (ostream& os, const pair<T,S>& p){return os << p.first << " " << p.second;}
  template<class T> ostream& operator << (ostream& os, const vector<T>& vec){for(size_t i=0; i<vec.size(); i++) os << vec[i] << (i==vec.size()-1?"":" "); return os;}
  template<class T> ostream& operator ,  (ostream& os, const T& val){ return os << " " << val;}

  template<class H> void print(const H& head){ cout << head; }
  template<class H, class ... T> void print(const H& head, const T& ... tail){ cout << head << " "; print(tail...); }
  template<class ... T> void println(const T& ... values){ print(values...); cout << endl; }

  template<class H> void eprint(const H& head){ cerr << head; }
  template<class H, class ... T> void eprint(const H& head, const T& ... tail){ cerr << head << " "; eprint(tail...); }
  template<class ... T> void eprintln(const T& ... values){ eprint(values...); cerr << endl; }

  class range{ Integer start_, end_, step_; public: struct range_iterator{ Integer val, step_; range_iterator(Integer v, Integer step) : val(v), step_(step) {} Integer operator * (){return val;} void operator ++ (){val += step_;} bool operator != (range_iterator& x){return step_ > 0 ? val < x.val : val > x.val;} }; range(Integer len) : start_(0), end_(len), step_(1) {} range(Integer start, Integer end) : start_(start), end_(end), step_(1) {} range(Integer start, Integer end, Integer step) : start_(start), end_(end), step_(step) {} range_iterator begin(){ return range_iterator(start_, step_); } range_iterator   end(){ return range_iterator(  end_, step_); } };

  inline string operator "" _s (const char* str, size_t size){ return move(string(str)); }
  constexpr Integer my_pow(Integer x, Integer k, Integer z=1){return k==0 ? z : k==1 ? z*x : (k&1) ? my_pow(x*x,k>>1,z*x) : my_pow(x*x,k>>1,z);}
  constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z=1){return k==0 ? z%M : k==1 ? z*x%M : (k&1) ? my_pow_mod(x*x%M,k>>1,M,z*x%M) : my_pow_mod(x*x%M,k>>1,M,z);}
  constexpr unsigned long long operator "" _ten (unsigned long long value){ return my_pow(10,value); }

  inline int k_bit(Integer x, int k){return (x>>k)&1;} //0-indexed

  mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count());

  template<class T> string join(const vector<T>& v, const string& sep){ stringstream ss; for(size_t i=0; i<v.size(); i++){ if(i>0) ss << sep; ss << v[i]; } return ss.str(); }

  inline string operator * (string s, int k){ string ret; while(k){ if(k&1) ret += s; s += s; k >>= 1; } return ret; }
}
constexpr long long mod = 9_ten + 7;

int solve(string s){
  int n = s.size();

  vector<vector<int>> cnt(n+1, vector<int>(26, 0));
  for(int i=0; i<n; i++){
    cnt[i+1][s[i]-'a'] += 1;
  }
  for(int i=1; i<=n; i++){
    for(int c=0; c<26; c++){
      cnt[i][c] += cnt[i-1][c];
    }
  }

  {
    int odd = 0;
    for(int i=0; i<26; i++){
      if(cnt[n][i]%2){
        odd += 1;
      }
    }
    if(odd <= 1){
      println(1);
      return 0;
    }
  }

  vector<int> dp(n+1, 1e7);
  dp[0] = 0;
  for(int i=1; i<=n; i++){
    for(int j=0; j<i; j++){
      int odd = 0;
      for(int k=0; k<26; k++){
        int b = cnt[i][k] - cnt[j][k];
        if(b%2) odd += 1;
      }
      if( odd <= 1){
        dp[i] = min(dp[i], dp[j]+1);
      }
    }
  }
  println(dp[n]);
  return 0;
}


int unko(string s){
  int n = s.size();

  vector<int> xsum(n+1, 0);
  for(int i=0; i<n; i++){
    xsum[i+1] = 1<<(s[i]-'a');
  }
  for(int i=1; i<=n; i++){
    xsum[i] ^= xsum[i-1];
  }

  vector<vector<int>> cnt(n+1, vector<int>(26, 0));
  for(int i=0; i<n; i++){
    cnt[i+1][s[i]-'a'] += 1;
  }
  for(int i=1; i<=n; i++){
    for(int c=0; c<26; c++){
      cnt[i][c] += cnt[i-1][c];
    }
  }

  {
    int odd = 0;
    for(int i=0; i<26; i++){
      if(cnt[n][i]%2){
        odd += 1;
      }
    }
    if(odd <= 1){
      println(1);
      return 0;
    }
  }

  map<int, vector<int>> memo;
  for(int i=0; i<=n; i++){
    memo[xsum[i]].push_back( i );
  }
  map<int, int> dp;
  for(auto p : memo){
    dp[p.first] = 1e7;
  }
  dp[0] = 0;

  int ans = 1e7;
  for(int i=0; i<n; i++){
    int v = xsum[i+1];
    for(int j=0; j<=26; j++){
      int bits = 1<<j;
      if(j==26) bits = 0;
      int target = v ^ bits;
      if(memo.count(target) == 0) continue;
      auto& vec = memo[target];
      auto itr = lower_bound(vec.begin(), vec.end(), i+1);
      if(itr == vec.begin()) continue;

      dp[v] = min(dp[v], dp[target]+1);

      if(i==n-1){
        ans = min(ans, dp[target]+1);
      }
    }
  }

  println(ans);

  return 0;
}

int main(){
  string s;
  cin >> s;

  // for(int i=1; i<=s.size(); i++){
  //   string t = s.substr(0, i);
  //   print(t, ":");
  //   solve(t);
  // }

  unko(s);
  return 0;
}


Measured memory_bytes: 59268