#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define endl "\n"
#define pq priority_queue<int>
#define rep(i,a,n) for(int i=a;i<n;i++)
#define debug1(x) cout<<x<<endl;
#define debug2(a,b) cout<<a<<" "<<b<<endl;
const int INF = 0x3f3f3f3f;//无穷大
const int inf = 0xc0c0c0c0;//无穷小
const int MOD = 1;
const int N = 1;

/*
 ________  ___  ___  ___  _______   ________ ________   ___  ________   ________
|\   ____\|\  \|\  \|\  \|\  ___ \ |\  _____\\   ___  \|\  \|\   ___  \|\   ____\
\ \  \___|\ \  \\\  \ \  \ \   __/|\ \  \__/\ \  \\ \  \ \  \ \  \\ \  \ \  \___|
 \ \  \    \ \   __  \ \  \ \  \_|/_\ \   __\\ \  \\ \  \ \  \ \  \\ \  \ \  \  ___
  \ \  \____\ \  \ \  \ \  \ \  \_|\ \ \  \_| \ \  \\ \  \ \  \ \  \\ \  \ \  \|\  \
   \ \_______\ \__\ \__\ \__\ \_______\ \__\   \ \__\\ \__\ \__\ \__\\ \__\ \_______\
    \|_______|\|__|\|__|\|__|\|_______|\|__|    \|__| \|__|\|__|\|__| \|__|\|_______|
                                                                                     */


void ChiefNing()
{
    int n;
    cin>>n;
    int tong[11][27],sum[27];
    memset(tong,0,sizeof(tong));
    int maxx=0;
    for(int i=0;i<n;i++){
        string s;
        getline(cin,s);
        int t1=s[4],t2=s[6],t3=s[8];
        if(t3=='a')tong[t1-'A'][t2-'A']=1;
    }
    memset(sum,0, sizeof(sum));
//    for(int i=0;i<27;i++)cout<<sum[i]<<" ";
    for(int i=0;i<27;i++){
        for(int j=0;j<11;j++){
            sum[i]+=tong[j][i];
        }
    }

    int ans=0;
    for(int i=0;i<27;i++){
        if(maxx<sum[i]){
            ans=i;
            maxx=sum[i];
        }
    }
    cout<<char(ans+'A')<<endl;
}

signed main(void)
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int _;
    cin>>_;
    while(_--)
        ChiefNing();
    return 0;
}