#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define xprintf(fmt,...) fprintf(stderr,fmt,__VA_ARGS__)
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(auto cnt=0ll;(cnt)<(l);++(cnt))
#define iterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);++(cnt))
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
#define EPS 1e-12
template<typename T1, typename T2> ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }
template<typename iterator> inline size_t argmin(iterator begin, iterator end) { return distance(begin, min_element(begin, end)); }
template<typename iterator> inline size_t argmax(iterator begin, iterator end) { return distance(begin, max_element(begin, end)); }
template<typename T> T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> T& minset(T& to, const T& val) { return to = min(to, val); }

mt19937_64 randdev(8901016);
inline ll rand_range(ll l, ll h) {
    return uniform_int_distribution<ll>(l, h)(randdev);
}

#ifdef __MAI
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
#ifdef __VSCC
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        inline MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
            return *this;
        }
        template<typename IT> void in(IT begin, IT end) {
            for (auto it = begin; it != end; ++it) *this >> *it;
        }
    };
}
MaiScanner scanner;


// 文字の個数をカウントして，0-1個が奇数，その他すべてが偶数ならば，回文が作れる

// dp[i] 

// L..Rで作れるなら，dp[R] = dp[L] + 1

ll m, n, kei;


string str;

int sum[200010][30];

int sumg[200010];


int dp[200010];

// 区間[L,R)で回文が作れるか
bool able(int l, int r) {
    int odd = 0;
    repeat(c, 'z' - 'a' + 1) {
        odd += sum[r][c] ^ sum[l][c];
    }
    return odd <= 1;
}


map<ll, int> nicedp;



int main() {

    scanner >> str;
    n = str.size();

    repeat(i, n) {
        sum[i + 1][str[i] - 'a'] = 1;
    }
    // 累積わ
    repeat(i, n) {
        repeat(j, 28) {
            sum[i + 1][j] ^= sum[i][j];
        }
    }

    // repeat(i, n) {
    //     int g = 0;
    //     repeat(j, 28) {
    //         g += sum[i][j];
    //     }
    //     sumg[i] = g <= 1;
    // }


    dp[0] = 0;
    nicedp[0] = 0;
    ll p = 0;
    iterate(i, 1, n + 1) {
        int right = i - 1;

        dp[i] = dp[i - 1] + 1;
        // repeat(left, i) {
        //     if (able(left, right + 1))
        //         minset(dp[i], dp[left] + 1);
        // }

        p ^= 1 << (str[right] - 'a');
        if (nicedp.count(p))
            minset(dp[i], nicedp[p] + 1);

        repeat(j, 26) {
            ll q = p ^ (1 << j);
            if (nicedp.count(q))
                dp[i] = min(dp[i], nicedp[q] + 1);
        }

        if (nicedp.count(p))
            minset(nicedp[p], dp[i]);
        else
            nicedp[p] = dp[i];
    }

    cout << dp[n] << endl;
    //debuga(dp, n + 3);
    //debugv(nicedp);

    return 0;
}

Measured memory_bytes: 37124