C

#include <bits/stdc++.h>

using namespace std;

#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int n;
        string s;
        cin>>n>>s;

        vector<int> cnt(26);

        for(auto e: s)
            cnt[e-'a']++;

        int mmax = *max_element(cnt.begin(), cnt.end());

        cout<<max(n%2, max(0, 2*mmax-n))<<"\n";
    }
}