#include <bits/stdc++.h>
#include "combo.h"
template <class T> using Vec = std::vector<T>;
constexpr char LET[] = {'A', 'B', 'X', 'Y'};
std::string guess_sequence(int N) {
if (N == 1) {
for (int k = 0; k < 3; ++k) {
std::string tmp{LET[k]};
if (press(tmp)) {
return tmp;
}
}
return std::string{LET[3]};
}
std::string cur;
cur.push_back([&] {
if (press("AB") == 0) {
return press("X") ? 'X' : 'Y';
} else {
return press("A") ? 'A' : 'B';
}
}());
Vec<int> other;
for (int i = 0; i < 4; ++i) {
if (LET[i] != cur[0]) {
other.push_back(i);
}
}
for (int i = 1; i < N - 1; ++i) {
std::string ask;
for (int k = 0; k < 3; ++k) {
ask += cur;
ask += LET[other[0]];
ask += LET[other[k]];
}
ask += cur;
ask += LET[other[1]];
cur += LET[other[2 - (press(ask) - i)]];
}
for (int k = 0; k < 2; ++k) {
std::string tmp = cur + LET[other[k]];
if (press(tmp) == N) {
return tmp;
}
}
return cur + LET[other[2]];
}
