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

const int inf = 1e9;

int n;
int p2[30];
char s[200005];
map<int,int> dp;

int get(int x) {
    if(dp.find(x)==dp.end()) return inf;
    return dp[x];
}

int main() {
    int cur;
    p2[0] = 1;
    for(int i=1;i<=26;i++) p2[i] = p2[i-1]*2;
    scanf(" %s",s);
    n = strlen(s); cur = 0; dp[0] = 0;
    for(int i=0;i<n;i++) {
        cur ^= p2[s[i]-'a'];
        int val = get(cur);
        for(int pos=0;pos<26;pos++) val = min(val,get(cur^p2[pos])+1);
        dp[cur] = val;
    }
    if(cur==0) printf("1");
    else printf("%d",get(cur));
}
