#include <bits/stdc++.h>
using namespace std;
int press(string p);
string first_char() {
string s = "A";
if (press(s)) return s;
s = "B";
if (press(s)) return s;
s = "X";
if (press(s)) return s;
s = "Y";
return s;
}
string guess_sequence(int N) {
string s = first_char();
int l = 1;
while (l != N) {
++l;
s += "A";
if (s[0] != 'A' && press(s) == l) continue;
s[l - 1] = 'B';
if (s[0] != 'B' && press(s) == l) continue;
s[l - 1] = 'X';
if (s[0] != 'X' && press(s) == l) continue;
s[l - 1] = 'Y';
}
return s;
}
