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

using namespace std;
using namespace __gnu_pbds;

string s;
cc_hash_table <int, int> H;

int main ()
{
	ios::sync_with_stdio(false);
	cin >> s;
	int stat = 0;
	int l = s.length();
	H[0] = 0;
	for (int i = 0; i < l; i++)
	{
		stat ^= (1 << (s[i] - 'a'));
		int mi = 123456789;
        if (H[stat] != 0)
		{
			continue;
		}
		for (int j = 0; j < 26; j++)
		{
			if (H[stat ^ (1 << j)] != 0)
			{
				mi = min(mi, H[stat ^ (1 << j)]);
			};
		}
		H[stat] = mi + 1;
	}
	if (!stat) cout << 1 << endl;
	else cout << H[stat] << endl;
	return 0;
}