#include <bits/stdc++.h>
#include "combo.h"
using namespace std;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define ll long long
#define ld long double
#define all(_v) _v.begin(), _v.end()
#define sz(_v) (int)_v.size()
#define pii pair <int, int>
#define pll pair <ll, ll>
#define veci vector <int>
#define vecll vector <ll>
bool check(char x) {
string s = "";
s += x;
int cnt = press(s);
if(cnt > 1 || !cnt) return 0;
return 1;
}
string guess_sequence(int n) {
string cur = "";
set <char> st;
st.insert('A');
st.insert('B');
st.insert('X');
st.insert('Y');
if(press("A")) cur = "A", st.erase('A');
else if(press("B")) cur = "B", st.erase('B');
else if(press("X")) cur = "X", st.erase('X');
else cur = "Y", st.erase('Y');
auto it = st.begin();
char a1, a2, a3;
a1 = *it;
++it;
a2 = *it;
++it;
a3 = *it;
for(int i = 1; i < n; ++i) {
if(i == n - 1) {
if(press(cur + a1) == n) cur += a1;
else if(press(cur + a2) == n) cur += a2;
else cur += a3;
} else {
int res = press(cur + a1 + cur + a2 + a1 + cur + a2 + a2 + cur + a2 + a3);
if(res == i) cur += a3;
else if(res == i + 1) cur += a1;
else if(res == i + 2) cur += a2;
}
}
return cur;
}
