#include "combo.h"
#include <bits/stdc++.h>
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; i++)
#define FORE(i, v) for (__typeof((v).begin()) i = (v).begin(); i != (v).end(); i++)
#define ALL(v) (v).begin(), (v).end()
#define IS_INF(x) (std::isinf(x))
#define IS_NAN(x) (std::isnan(x))
#define fi first
#define se second
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define div ___div
#define prev ___prev
#define next ___next
#define left ___leftc
#define right ___right
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define __Im_sogood__ main()
#define __builtin_popcount __builtin_popcountll
using namespace std;
const int MAXN = 2e5 + 5;
int n, a[MAXN];
int press(string p);
char getBeginChar() {
int ans = press("AB"); if(ans > 0) {
if(press("A") == 1) return 'A'; return 'B';
}
if(press("X") == 1) return 'X'; return 'Y';
}
string guess_sequence(int N) {
if(N == 1) {
if(press("A") == 1) return "A";
if(press("B") == 1) return "B";
if(press("X") == 1) return "X";
return "Y";
}
char f = getBeginChar(); vector<string> againstChar;
if('A' != f) againstChar.push_back("A");
if('B' != f) againstChar.push_back("B");
if('X' != f) againstChar.push_back("X");
if('Y' != f) againstChar.push_back("Y"); string pre = ""; pre += f;
int M = 0; REP(i, N - 2) {
string mergeString = pre + againstChar[0] + pre +
againstChar[1] + againstChar[0] + pre + againstChar[1] + againstChar[1] +
pre + againstChar[1] + againstChar[2];
M = (int)pre.size(); int answer = press(mergeString);
if(answer == M + 1) pre += againstChar[0];
else if(answer == M + 2) pre += againstChar[1]; else {
pre += againstChar[2];
}
}
// we need to search all of char to guess the last digit
// n - 2 + 2
// need to use 3 query to solve against
REP(i, againstChar.size() - 1) {
string mergeString = pre + againstChar[i]; if(press(mergeString) == N) {
return mergeString;
}
}
//cout << "before ans\n";
//FORE(it, againstChar) cout << (*it) << endl;
return pre + againstChar.back();
}
/*__Im_sogood__{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cout << guess_sequence(3);
cerr << "Time elapsed: " << TIME << " s.\n";
return 0;
}*/
