A. Special Characters.cpp

#include <bits/stdc++.h>
#define int long long
#define vi vector<int>
#define vb vector<bool>
#define readInput(a) \
  for (auto &i : a)  \
  cin >> i
#define printOutput(a) \
  for (auto &i : a)    \
  cout << i << " "
#define endLine "\n"
#define space << " " <<
#define pushBack pb
#define allElements(a) a.begin(), a.end()
#define reverseAll(a) a.rbegin(), a.rend()
const int N = 1e6 + 2;
const int MOD = 1e9 + 7;
const int INF = LLONG_MAX;
using namespace std;

signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t; cin >> t;

  while (t--) {
    int  n;cin>>n;


    // cout<<(char(1 +'A'))<<endl;

    if(n%2){
      cout<<"NO"<<endl;
      continue;
    }

    cout<<"YES"<<endl;
    int cnt=0;
    for(int i=0;i<n/2;i++){
      cout<<(char(cnt +'A'))<<(char(cnt +'A'));
      cnt++;
    }

    cout<<endl;

  

  }
}