#include <bits/stdc++.h>
using namespace std;
int press(string p);
vector < char > aux;
string first_char() {
string s = "AB";
int ans = press(s);
if (ans == 2) {
aux = {'B', 'X', 'Y'};
return s;
}
if (ans) {
s = "A";
if (press(s)) {
aux = {'B', 'X', 'Y'};
return s;
}
aux = {'A', 'X', 'Y'};
return "B";
}
s = "X";
if (press(s)) {
aux = {'A', 'B', 'Y'};
return s;
}
aux = {'A', 'B', 'X'};
return "Y";
}
string guess_sequence(int N) {
string s = first_char();
for (int i = (int)s.size() + 1; i <= N; ++i) {
s += aux[0];
if ((i != 2 || s[0] != 'A') && press(s) == i) continue;
s[i - 1] = aux[1];
if ( press(s) == i) continue;
s[i - 1] = aux[2];
}
return s;
}
