#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1005;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    ll t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        set<string>mp;
        map<char,int>mmp;
        int x=0;
        char y=65;
        while(n--){
            string a,c,d;
            char b;
            cin>>a>>b>>c;
            if(c[0]=='a'){
                d=a+b+c;//就是判断是否重复
               auto it=mp.find(d);
               if(it==mp.end()){
                mmp[b]++;
               }
            }
        }
          for(auto [key,val]:mmp){
            if(val>x){
                y=key;
            }
           }
       cout<<y<<"\n";
    }
    return 0;
}