#include <bits/stdc++.h>
#include "combo.h"
#define TASK "task"
#define INT_LIM (int) 2147483647
#define LL_LIM (long long) 9223372036854775807
#define endl '\n'
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define BIT(i,x) (((i)>>(x))&1)
#define FOR(i,a,b) for(int i = (a); i<=(b); i++)
#define FORD(i,a,b) for(int i = (a); i>=(b); i--)
#define ll long long
#define pii pair<int,int>
using namespace std;
///------------------------------------------///
//int press(string p)
//{
// return 0;
//}
char binarysearch(int i, string cur)
{
if (press(cur+"A"+cur+"B")==i)
{
if (press(cur+"A")==i) return 'A';
return 'B';
}
if (press(cur+"X")==i) return 'X';
return 'Y';
}
string guess_sequence(int N)
{
string ret = "";
vector<char> digit = {'A', 'B', 'X', 'Y'};
if (N==3)
{
FOR(i, 1, 3)
{
for (auto d:digit)
{
ret+= d;
if (press(ret)==i) break;
ret.pop_back();
}
}
return ret;
}
ret+= binarysearch(1, ret);
if (N==1) return ret;
char c[3]; int cnt = 0;
for (auto d:digit) if (d!=ret[0])
{
c[cnt++] = d;
}
FOR(i, 2, N-1)
{
string tmp = ret+c[0]+ret+c[1]+c[0]+ret+c[1]+c[1]+ret+c[1]+c[2];
int result = press(tmp);
if (result==i) ret+= c[0];
else if (result==i+1) ret+= c[1];
else ret+= c[2];
}
ret+= binarysearch(N, ret);
return ret;
}
//signed main()
//{
// ///--------------------------///
// ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
// if (fopen(TASK".INP","r")!=NULL)
// {
// freopen(TASK".INP","r",stdin);
// freopen(TASK".OUT","w",stdout);
// }
// ///--------------------------///
//
// int NTEST = 1;
// //cin >> NTEST;
//
// return 0;
//}
//
/////------------------------------------------///
