#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
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 {
coin = press(q);
};
string st = "Y";
string s = st;
rep(i, 0, sz(l) - 1) {
query(string(n, l[i]));
if (coin > 0) {
s = "";
s += l[i];
break;
}
}
vector<char> chars;
trav(c, l) if (c != s[0]) chars.pb(c);
rep(i, 0, n-1) {
shuffle(all(chars), rnd);
bool found = 0;
rep(j, 0, sz(chars) - 1) {
string temp = s;
temp += chars[0];
while(sz(temp) < n) temp += st;
query(temp);
if (coin == sz(s) + 1) {
s += chars[0];
found = 1;
continue;
}
}
if (!found) s += chars[1];
}
return s;
}
