#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <set>
#include <iterator>
#include <stack>
#include <map>
#include <math.h>
#include <bitset>
#include <deque>
#include <string>
#include <tuple>
#include <queue>
#include <numeric>
#include <unordered_set>
#include <unordered_map>
#define pi 3.141592653589793238
#define ll long long
#define ld long double
#define rep(i, a, b) for (long long i = a; i <= b; i++)
#define mod 1000000007ll
#define INF 1000000000000000000
#define pb push_back
#define ff first
#define ss second
#define endl '\n'
#define all(x) (x).begin (), (x).end ()
#define sz(x) (ll) (x).size ()
#define reunique(v) v.resize(std::unique(v.begin(), v.end()) - v.begin())
#define rank rnk
#define log lg
#define fast \
ios_base::sync_with_stdio (false); \
cin.tie (NULL); \
cout.tie (NULL)
using namespace std;
int press(string p);
string guess_sequence(int n)
{
string ans="";
vector <char> pos={'A','B','X','Y'};
for(auto c:pos)
{
string q="";
q.pb(c);
int x=press(q);
if(x==1)
{
ans.pb(c);
break;
}
}
while(sz(ans)!=n)
{
for(auto c:pos)
if(c!=ans[0])
{
string q=ans;
q.pb(c);
int x=press(q);
if(x==sz(ans)+1)
{
ans.pb(c);
break;
}
}
}
return ans;
}
// signed main()
// {
// fast;
// freopen("milkorder.in","r",stdin);
// freopen("milkorder.out","w",stdout);
// guess_sequence(5);
// return 0;
// }
