#include <bits/stdc++.h>
using namespace std ;

const int magic = 26 , N = (1<<magic) + 5 ;
const int maxn = 2e5 + 5 ;

int dp[N] , res[N] ;


int main () {

    int n ;
    string s ;
    cin >> s ;
    n = s.size() ;
    s = "#" + s ;
    for (int i = 1 ; i < N ; i++) {
        dp[i] = (1<<26) ;
    }
    dp[0] = 0 ;
    int cur = 0 ;
    for (int i = 1 ; i <= n ; i++) {
        int bit = s[i]-'a' ;
        cur ^= (1<<bit) ;
        res[i] = dp[cur] + 1 ;
        for (int j = 0 ; j < 26 ; j++) {
            int nw = cur^(1<<j) ;
            res[i] = min(res[i],dp[nw] + 1) ;
        }
        dp[cur] = min(dp[cur],res[i]) ;
    }
    cout << res[n] << endl ;
}
