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#include <bits/stdc++.h>
//#include "boxes.h"
//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
//#pragma GCC target("avx,tune=native")

using namespace std;

typedef long long ll;

typedef long double ld;

ll AR = 19, BR = 13, CR = 23, XR = 228, YR = 322, MODR = 1e9 + 993;

ll myrand(){
    ll ZR = (XR * AR + YR * BR + CR) % MODR;
    XR = YR;
    YR = ZR;
    return ZR;
}

const int mod = 1e9 + 7;

ll bpow(ll x, ll y){
    if (y == 0)
        return 1;
    if (y == 1)
        return x;
    ll ret = bpow(x, y >> 1);
    ret = (ret * ret) % mod;
    if (y & 1)
        ret = (ret * x) % mod;
    return ret;
}

ll bdiv(ll x, ll y){
    return (x * bpow(y, mod - 2)) % mod;
}

const ll llinf = 2e18 + 100;

const int maxn = 2e5 + 100, inf = 1e9 + 100, sq = 300;

int n;

string s;

int q[(1 << 26) + 100];

int main()
{
    #ifdef ONPC
    //ifstream cin("a.in");
    //ofstream cout("a.out");
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
    #else
    //ifstream cin("a.in");
    //ofstream cout("a.out");
    //freopen("trap.in", "r", stdin);
    //freopen("trap.out", "w", stdout);
    #endif // ONPC
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> s;
    n = s.size();
    q[0] = 1;
    int mask = 0;
    for (int i = 0; i < n; i++){
        mask ^= (1 << (s[i] - 'a'));
        int ans = inf;
        if (q[mask] != 0)
            ans = q[mask];
        for (int j = 0; j < 26; j++){
            mask ^= (1 << j);
            if (q[mask] != 0)
                ans = min(ans, q[mask]);
            mask ^= (1 << j);
        }
        if (q[mask] == 0)
            q[mask] = ans + 1;
        else
            q[mask] = min(q[mask], ans + 1);
        if (i == n - 1){
            cout << ans;
            return 0;
        }
    }
}


Measured memory_bytes: 262420