https://ioi.contest.codeforces.com/group/32KGsXgiKA/contest/103776/problem/A

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define pb push_back
string guess_sequence(int N){
	string ans="";
	for(int i=1;i<=N;i++){
		int z=press(ans+'A');
		int k=ans.size();
		if(z==k+1){
			ans+='A';
			continue;
		}
		z=press(ans+'B');
		if(z==k+1){
			ans+='B';
			continue;
		}
		z=press(ans+'X');
		if(z==k+1){
			ans+='X';
			continue;
		}
		z=press(ans+'Y');
		if(z==k+1){
			ans+='Y';
			continue;
		}
	}
	return ans;
}