#include "combo.h"
#include <bits/stdc++.h>
using namespace std;
string guess_sequence(int n) {
string ans;
ans.reserve(n);
array a = {'A', 'B', 'X', 'Y'};
// call `press` 2 times
auto guess_endpoint = [&]() {
if (press(ans + a[0] + ans + a[1]) == int(ans.size()))
ans += press(ans + a[2]) == int(ans.size()) ? a[3] : a[2];
else
ans += press(ans + a[0]) == int(ans.size()) ? a[1] : a[0];
};
auto guess_mid = [&]() {
if (const auto cnt = press(ans + a[0] + a[0] + ans + a[0] + a[1] + ans + a[0] + a[2] + ans + a[1]);
cnt == 0)
ans += a[2];
else if (cnt == 1)
ans += a[1];
else
ans += a[0];
};
// call `press` 2 + (n - 2) + 2
// first
guess_endpoint();
if (n == 1) return ans;
*find(a.begin(), a.end(), ans[0]) = 'Y';
// n - 2
for (int i = n - 2; i; --i)
guess_mid();
// last
if (n != 1) guess_endpoint();
return ans;
}
