#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 = "Y";
rep(i, 0, sz(l) - 1) {
query(string(n, l[i]));
if (coin > 0) {
s = "";
s += l[i];
break;
}
}
char st = s[0];
dbg(st);
dbg("step 1 done");
vector<char> chars;
trav(c, l) if (c != st) chars.pb(c);
assert(sz(chars) == 3);
rep(i, 0, n-1) {
shuffle(all(chars), rnd);
rep(j, 0, 3) {
dbg(chars[j]);
}
bool found = 0;
rep(j, 0, 2) {
string temp = s;
temp += chars[j];
while(sz(temp) < n) temp += st;
query(temp);
if (coin == sz(s) + 1) {
s += chars[j];
found = 1;
break;
}
}
if (!found) s += chars[2];
}
return s;
}
