#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define all(x) x.begin(), x.end()
#define F first
#define ld long double
#define S second
using namespace std;
const ll N = 5e3 + 5;
const ll NN = 4e5 + 5;
const ll INF = 1e18;
const ll inf = 1e9;
const ll MOD = 1e9 + 7;
char a[10];
int was[10];
int press(std::string p);
string guess_sequence(int n){
a[1] = 'A';
a[2] = 'B';
a[3] = 'X';
a[4] = 'Y';
string s = "";
for(int i = 1;i <= 4;i++){
string d = "";
d += a[i];
int res = press(d);
if(res == 1){
s = d;
for(int j = i;j <= 3;j++){
a[j] = a[j + 1];
}
break;
}
}
for(int i = 2;i <= n;i++){
if(int(s.size()) > i)continue;
string d = s;
d += a[1];
d += a[2];
int res = press(d);
int sz= int(s.size());
if(res == sz){
s += a[3];
}
else if(res == sz + 1){
d = s;
d += a[1];
res = press(d);
if(res == sz + 1){
s = d;
}
else{
s += a[2];
}
}
else{
s = d;
}
}
return s;
}
