#include <bits/stdc++.h>
#include "combo.h"
// #include "grader.cpp"
using namespace std;
string guess_sequence(int n) {
string s;
vector<string> v = {"A", "B", "X", "Y"};
for (int i = 0; i < 4; i++) {
if (i == 3 || press(v[i])) {
s += v[i];
v.erase(v.begin() + i);
break;
}
}
for (int i = 1; i < n - 1; i++) {
string t = s + v[1];
for (auto j : v)
t += s + v[2] + j;
for (auto j : t)
assert(j == 'A' || j == 'B' || j == 'X' || j == 'Y');
assert((int)t.size() <= 4 * n);
s += v[press(t) - i];
}
for (auto i : v) {
s += i;
assert((int)s.size() == n);
if (i == v.back() || press(s) == n) return s;
s.pop_back();
}
assert(false);
}
