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

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    string s;
    int n;
    cin >> s;
    n = s.size();
    static int xs[200001];
    for(int i=0;i<n;++i) xs[i+1] = 1 << (s[i]-'a');
    for(int i=0;i<n;++i) xs[i+1] ^= xs[i];
    if(__builtin_popcount(xs[n]) <= 1){ cout << 1 << endl; return 0; }
    static int dp[1<<26];
    for(int i=0;i<(1<<26);++i) dp[i] = INT32_MAX / 2;
    dp[0] = 0;
    for(int i=1;i<=n;++i){
        for(int j=0;j<='z'-'a';++j) dp[xs[i]] = min(dp[xs[i]], dp[xs[i]^(1<<j)]+1);
    }
    cout << dp[xs[n]] << endl;
   
    return 0;
}