#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 200001;

string s;
int cur[MX],dp[MX];
map<int,int> lst;

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> s;
    int ind = 0;
    for (char c: s) {
        ind ++;
        cur[ind] = cur[ind-1]^(1<<(c-'a'));
        lst[cur[ind]] = ind;
    }
    F0Rd(i,sz(s)) {
        dp[i] = MOD;
        F0R(j,26) {
            int CUR = cur[i]^(1<<j);
            if (lst.count(CUR) && lst[CUR] > i)  dp[i] = min(dp[i],dp[lst[CUR]]+1);
        }
        if (lst.count(cur[i]) && lst[cur[i]] > i) dp[i] = min(dp[i],dp[lst[cur[i]]]+1);
    }
    cout << dp[0];
}

// read the question correctly (is y a vowel? what are the exact constraints?)
// look out for SPECIAL CASES (n=1?) and overflow (ll vs int?) ARRAY OUT OF BOUNDSS