#include <bits/stdc++.h>
using namespace std;
string charset = "ABXY";
int root;
vector<int> others;
string prefix;
int press(string p);
string guess_sequence(int N){
// Find "root"
{
int res1 = press("AB");
if (res1 > 0){
int res2 = press("A");
if (res2 > 0) root = 0;
else root = 1;
}
else{
int res2 = press("X");
if (res2 > 0) root = 2;
else root = 3;
}
}
others.clear();
// Init
for (int i = 0; i < 4; i++){
if (i != root) others.push_back(i);
}
string s0 = string(1, charset[others[0]]), s1 = string(1, charset[others[1]]),
s2 = string(1, charset[others[2]]), sr = string(1, charset[root]);
// Find N-2 middle characters
prefix = charset[root];
for (int i = 1; i < N-1; i++){
vector<string> added;
added.push_back(s0 + s0);
added.push_back(s0 + s1);
added.push_back(s0 + s2);
added.push_back(s1 + sr);
string query = "";
for (auto s: added) query += prefix + s;
int r = press(query);
if (r == i+2) prefix += s0;
else if (r == i+1) prefix += s1;
else prefix += s2;
}
if (N >= 2){
int res1 = press(prefix + s0);
if (res1 == N) prefix += s0;
else{
int res2 = press(prefix + s1);
if (res2 == N) prefix += s1;
else prefix += s2;
}
}
return prefix;
}
