#include "bits/stdc++.h"
using namespace std;
const int maxn = 26;
const int sz = 200100;
int ls[1<<maxn], dp[sz];
int M(){
    string s;
    if(!(cin >> s)) return 0;
    for(int e = 0; e < 1<<maxn; e++) ls[e] = sz;
    int my = 0;
    dp[0] = 0;
    ls[0] = 0;
    for(int e = 0; e < s.size(); e++){
        my ^= 1<<(s[e] - 'a');
        dp[e+1] = 1 + dp[e];
        for(int f = 0; f < 26; f++){
            int mask = 1<<f;
            mask ^= my;
            dp[e+1] = min(dp[e+1], ls[mask] + 1);
        }
        dp[e+1] = min(dp[e+1], ls[my] + 1);
        ls[my] = min(ls[my], dp[e+1]);
    }
    cout << dp[s.size()] << endl;
    return 1;
}
int main(){
    while(M());
    return 0;
}
