#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define ii pair<int, int>
#define vi vector<int>
#define ff first
#define ss second
#define sz(a) (int)a.size()
#define fto(i, a, b) for (int i = a; i <= b; ++i)
#define fdto(i, a, b) for (int i = a; i >= b; --i)
#define ll long long
#define oo 1000000007
#define maxN 100005
#define maxM 3
using namespace std;
int press(string p);
string guess_sequence(int n) {
vector<char> chr = {'A', 'B', 'X', 'Y'};
string s = "";
string p = "";
fto(i, 0, n-1) s += 'A', p += 'A';
fto(i, 0, n-1) {
fto(j, 0, 3) {
p[i] = chr[j];
int chk = press(p);
if (chk == sz(p)) s[i] = p[i];
}
}
return s;
}
