#include "combo.h"
#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define FOR(i, a, b) for(int i = (a), _b = (b); i <= _b; ++i)
#define REP(i, a, b) for(int i = (a), _b = (b); i >= _b; --i)
#define mp make_pair
#define all(v) v.begin(), v.end()
#define uni(v) v.erase(unique(all(v)), v.end())
#define Bit(x, i) ((x >> (i)) & 1)
#define Mask(i) (1 << (i))
#define Cnt(x) __builtin_popcount(x)
#define Cntll(x) __builtin_popcountll(x)
#define Ctz(x) __builtin_ctz(x) // so luong so 0 tinh tu ben phai
#define Ctzll(x) __builtin_ctzll(x)
#define Clz(x) __builtin_clz(x) // so luong so 0 tinh tu ben trai
#define Clzll(x) __builtin_clzll(x)
inline bool maximize(int &u, int v){
return v > u ? u = v, true : false;
}
inline bool minimize(int &u, int v){
return v < u ? u = v, true : false;
}
inline bool maximizell(long long &u, long long v){
return v > u ? u = v, true : false;
}
inline bool minimizell(long long &u, long long v){
return v < u ? u = v, true : false;
}
const int mod = 1e9 + 7;
inline int fastPow(int a, int n){
if(n == 0) return 1;
int t = fastPow(a, n >> 1);
t = 1ll * t * t % mod;
if(n & 1) t = 1ll * t * a % mod;
return t;
}
inline void add(int &u, int v){
u += v;
if(u >= mod) u -= mod;
}
inline void sub(int &u, int v){
u -= v;
if(u < 0) u += mod;
}
const int maxN = 2e5 + 5;
const int inf = 1e9;
const long long infll = 1e18;
//string ords;
//int N;
//int press(string p){
// int answer = 0;
// for(int t = 0; t < p.size(); ++t){
// int j = t, i = 0;
// while(j < p.size() && i < N && ords[i] == p[j]){
// ++i;
// ++j;
// }
// maximize(answer, j - t);
// }
// return answer;
//}
char c[] = {'A', 'B', 'X', 'Y'};
string t[] = {"A", "B", "X", "Y"};
string guess_sequence(int n){
string s = "";
char ban = 'Z';
int cnt = 0;
FOR(i, 0, 2){
// ++cnt;
if(press(t[i]) == 1){
s = t[i];
ban = c[i];
break;
}
}
if(ban == 'Z') s = t[3], ban = c[3];
if(n == 1) return s;
FOR(i, 1, n - 1) s += 'Z';
FOR(i, 1, n - 1){
vector<char> imp;
FOR(j, 0, 3){
if(c[j] == s[i - 1] || c[j] == s[0]) continue;
imp.emplace_back(c[j]);
}
ban = 'Z';
for(int j = 0; j < (int)imp.size() - 1; ++j){
// ++cnt;
FOR(t, i, n - 1)s[t] = imp[j];
int x = press(s);
assert(x >= i);
if(x > i){
FOR(t, i, x - 1)s[i] = imp[j];
ban = imp[j];
break;
}
}
if(ban == 'Z'){
// ++cnt;
FOR(t, i, n - 1)s[t] = imp.back();
int x = press(s);
assert(x > i);
i = x - 1;
ban = imp.back();
}
}
// cout << cnt << '\n';
return s;
}
//void process(){
// cin >> ords;
// N = ords.size();
// string answer = guess_sequence(N);
// cout << ords << '\n' << answer;
//}
//#define LOVE ""
//int main(){
// if(fopen(LOVE".inp", "r")){
// freopen(LOVE".inp", "r", stdin);
// freopen(LOVE".out", "w", stdout);
// }
// ios_base::sync_with_stdio(false);
// cin.tie(0);
// cout.tie(0);
//
// int t = 1;
//// cin >> t;
// while(t--)
// process();
//// cerr << '\n' << "Time elapsed: " << (1.0 * clock() / CLOCKS_PER_SEC) << " s\n" ;
// return 0;
//}
