//ΔATCODER QUALC D
#include<iostream>
#include<cstdio>
#include<fstream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<cmath>
#include<cstring>
#include<cstdlib>
using namespace std;
typedef long long LL;
const int N = 222222;
const int M = 26;
map<int,int> S;
char ch[N];
int a[N],dp[N];
int main()
{
	int n,i,j,x,y;
	cin>>ch;
	n=strlen(ch);
	x=0;
	S[0]=0;
	for(i=1;i<=n;i=i+1){
		a[i]=ch[i-1]-'a';
		x^=(1<<a[i]);
		if(S.find(x)==S.end())
			S[x]=N;
		dp[i]=S[x]+1;
		for(j=0;j<M;j=j+1){
			y=x^(1<<j);
			if(S.find(y)!=S.end())
				dp[i]=min(dp[i],S[y]+1);
		}
		if(S[x]>dp[i])
			S[x]=dp[i];
	}
	cout<<dp[n]<<endl;
	return 0;
}