#include <bits/stdc++.h>
#include "combo.h"
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define trav(a, x) for (auto &a : x)
#define pb push_back
//#define dbg(x) cout << #x << " = " << x << endl
#define dbg(x)
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
string guess_sequence(int N) {
ll n = N;
vector<char> l = {'A', 'B', 'X', 'Y'};
int coin;
auto query = [&](string q) -> void {
//dbg(q);
coin = press(q);
};
string s;
query("AB");
if (coin) {
query("A");
s = (coin ? "A" : "B");
}
else {
query("X");
s = (coin ? "X" : "Y");
}
char st = s[0];
if (n == 1) return s;
vector<char> chars;
trav(c, l) if (c != st) chars.pb(c);
assert(sz(chars) == 3);
rep(i, 0, n-2) {
shuffle(all(chars), rnd);
string cur = "";
cur += s;
cur += chars[0];
rep(j, 0, sz(chars)) {
cur += s;
cur += chars[1];
cur += chars[j];
}
query(cur);
if (coin == sz(s)) s += chars[2];
else if (coin == sz(s) + 1) s += chars[0];
else s += chars[1];
}
shuffle(all(chars), rnd);
rep(i, 0, sz(chars) - 1) {
string cur = s;
cur += chars[i];
query(cur);
if (coin == sz(s) + 1) {
return cur;
}
}
return (s + chars[2]);
}
