#include <iostream>
#include <cstdio>
#include <vector>
#include <array>
#include <string>
#include <algorithm>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <cmath>
#include <climits>
#include <iomanip>
#include <limits>
#include <tuple>
#include <stack>
#include <bitset>
#include <cstring>
#include <sstream>
#include <functional>
#include <random>
#include "combo.h"
using namespace std;
string guess_sequence(int N) {
string ans;
for (char c : {'A', 'B', 'X'}) {
if (press(string(1, c))) {
ans.push_back(c);
break;
}
}
if (!ans.size())
ans.push_back('Y');
if (N == 1)
return ans;
char p[3];
int k = 0;
for (char c : {'A', 'B', 'X', 'Y'})
if (c != ans[0])
p[k++] = c;
for (int i = 1; i < N - 1; i++) {
int mx = (4*N - 12) / 4;
string suf = ans.size() <= mx
? ans
: ans.substr(ans.size() - mx);
string ask;
ask += suf; ask += p[0];
ask += suf; ask += p[1]; ask += p[0];
ask += suf; ask += p[1]; ask += p[1];
ask += suf; ask += p[1]; ask += p[2];
int q = press(ask);
if (q == ans.size() + 2) ans.push_back(p[1]);
else if (q == ans.size() + 1) ans.push_back(p[0]);
else ans.push_back(p[2]);
}
for (int i = 0; i < 2; ++i)
if (press(ans + p[i]) == N)
return ans + p[i];
return ans + p[2];
}
