#include <bits/stdc++.h>
using namespace std;
#define pb push_back
int press(string s);
string guess_sequence(int n) {
char hrf[4] = {'A', 'B', 'X', 'Y'};
char bas = '1';
for(auto &p : hrf) {
string s = "";
s.pb(p);
if(press(s) == 1) {
bas = p;
break;
}
}
string s = "";
s.pb(bas);
set<char> pre;
while(s.size() != n) {
string sub = s;
string test = "";
for(auto &p : hrf) {
if(p == bas || pre.count(p)) continue;
map< int , int > m;
while(test.size() + sub.size() + 1 < 4*n && sub.size() <= n) {
sub.pb(p);
m[sub.size()] = test.size();
test += sub;
}
int say = press(test);
if(say == s.size()) {
pre.insert(p);
break;
}
s = test.substr(m[say], say);
pre.clear();
pre.insert(p);
break;
}
}
return s;
}
