#include "bits/extc++.h"
using namespace std;
template <typename T>
void dbgh(const T& t) {
cerr << t << endl;
}
template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
cerr << t << " | ";
dbgh(u...);
}
#ifdef DEBUG
#define dbg(...) \
cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]: "; \
dbgh(__VA_ARGS__);
#else
#define dbg(...)
#define cerr \
if (false) \
cerr
#endif
#define endl "\n"
#define long int64_t
#define sz(x) int((x).size())
int press(string p);
const string chars = "ABXY";
char solve1(string s) {
string poss;
if (press(s + 'A' + s + 'B') > sz(s)) {
poss = "AB";
} else {
poss = "XY";
}
if (press(s + poss[0]) > sz(s)) {
return poss[0];
} else {
return poss[1];
}
}
string guess_sequence(int n) {
char first = solve1("");
string cchars;
for (auto& a : chars) {
if (a != first) {
cchars += a;
}
}
string s {first};
for (int i = 1; i < n - 1; i++) {
string buf = s + cchars[0];
for (auto& a : cchars) {
buf += s + cchars[1] + a;
}
dbg(buf, sz(buf), n);
int cans = press(buf);
if (cans == sz(s)) {
s += cchars[2];
} else if (cans == sz(s) + 1) {
s += cchars[0];
} else {
s += cchars[1];
}
}
return s + solve1(s);
}
