// #define LOCAL 1
#include <bits/stdc++.h>
#ifndef LOCAL
#include "combo.h"
#endif
using namespace std;
#define REP(i, n) for (int i = 0; i < (n); i++)
#ifdef LOCAL
int press(string s);
#endif
const int M = 4;
char ABC[] = "ABXY";
char REM[3];
string guess_sequence(int N) {
string s;
if (press("AB")) {
if (press("A")) {s += "A";}
else {s += "B";}
} else {
if (press("X")) {s += "X";}
else {s += "Y";}
}
{
int idx = 0;
REP(i, M) {
if (s[0] != ABC[i]) {REM[idx++] = ABC[i];}
}
}
REP(i, N-2) {
string ns = s + REM[0] + REM[0] +
s + REM[0] + REM[1] +
s + REM[0] + REM[2] + s + REM[1];
int q = press(ns);
if (q == i+3) {s += REM[0];}
else if (q == i+2) {s += REM[1];}
else {s += REM[2];}
}
if (N > 1) {
REP(j, M-2) {
if (press(s + REM[j]) == N) {s += REM[j]; break;}
}
if (s.length() < N) {s += REM[M-2];}
}
return s;
}
#ifdef LOCAL
string SECRET = "X";
int calls = 0;
int press(string p) {
calls++;
assert(p.length() <= SECRET.length() * 4);
const int m = p.length();
const int n = SECRET.length();
int lpref = 0;
REP(i, m) {
int j = 0;
while (j < n && i+j < m && SECRET[j] == p[i+j]) {j++;}
lpref = max(lpref, j);
}
return lpref;
}
int main() {
cout << guess_sequence(SECRET.length()) << '\n';
assert(calls <= (SECRET.length() + 2));
}
#endif
