#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cassert>
using namespace std;
inline bool operator == (string &a, string &b)
{
if(a.size() != b.size()) return 0;
for(int i = 0 ; i < a.size() ; ++i)
{
if(a[i] != b[i])
{
return 0;
}
}
return 1;
}
int press(string p);
string guess_sequence(int N)
{
string res = "";
string letters = "";
if (press("A")) res = "A";
else if (press("B")) res = "B";
else if (press("X")) res = "X";
else res = "Y";
for(string s : {"A", "B", "X", "Y"})
{
if(s == res) continue;
letters += s;
}
assert(letters.size() == 3);
for(int i = 1 ; i < N - 1 ; ++i)
{
int ans = press(res + letters[0] +
res + letters[1] + letters[0] +
res + letters[1] + letters[1] +
res + letters[1] + letters[2]);
int len = i;
if (ans == len + 1) ans += letters[0];
else if (ans == len + 2) ans += letters[1];
else ans += letters[2];
}
if (press(res + "A") == N) res += "A";
else if (press(res + "B") == N) res += "B";
else if (press(res + "X") == N) res += "X";
else res += "Y";
assert(res.size() == 1);
return res;
}
