#include "combo.h"
#include<bits/stdc++.h>
#define X first
#define Y second
#define all(x) begin(x), end(x)
#define FOR(i, a, b) for(int i = (a); i <= (b); i++)
#define FORD(i, b, a) for(int i = (b); i >= (a); i--)
#define REP(i, a, b) for (int i = (a); i < (b); i++)
#define mxx max_element
#define mnn min_element
#define SQR(x) (1LL * (x) * (x))
#define MASK(i) (1LL << (i))
#define Point Vector
#define left Left
#define right Right
#define div Div
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
typedef pair<db, db> pdb;
typedef pair<ld, ld> pld;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
typedef pair<ll, ll> pll;
typedef pair<ll, pll> plll;
typedef pair<ll, int> pli;
typedef pair<ll, pii> plii;
template<class A, class B>
bool maximize(A& x, B y) {
if (x < y) return x = y, true; else return false;
}
template<class A, class B>
bool minimize(A& x, B y) {
if (x > y) return x = y, true; else return false;
}
/* END OF TEMPLATE */
string guess_sequence(int n) {
// guess the first
string res = "";
if (press("AB") > 0) {
if (press("A") > 0) res+="A"; else res+="B";
}
else {
if (press("X") > 0) res+="X"; else res+="Y";
}
vector<char> tmp;
if ('A' != res[0]) tmp.push_back('A');
if ('B' != res[0]) tmp.push_back('B');
if ('X' != res[0]) tmp.push_back('X');
if ('Y' != res[0]) tmp.push_back('Y');
FOR(i, 2, n) {
if (i == n) {
int cnt = 0;
for (auto x : tmp) {
cnt++;
if (cnt == 3) break;
if (press(res + x) == i) {
res+=x;
break;
}
}
if (cnt == 3) res+=tmp.back();
}
else {
string ans = "";
REP(i, 0, 3) ans+=res + tmp[0] + tmp[i];
ans+=res + tmp[1];
int t = press(ans);
if (t == (int)res.size()) res+=tmp[2]; else
if (t == (int)res.size() + 1) res+=tmp[1]; else res+=tmp[0];
}
// cerr<<"find : "<<res<<endl;
}
return res;
}
