#include <bits/stdc++.h>
#include "combo.h"
#define lint long long
#define rep(i,n) for(int i = 0; i < n; i++)
#define all(a) a.begin(), a.end()
using namespace std;
/*
int press(string a){
cout << a <<"\n";
int res;
cin>>res;
return res;
} */
string guess_sequence(int n){
string val = "ABXY";
string cur;
if(press("AB")>=1){
if(press("A")){
cur="A";
} else {
cur="B";
}
} else
{
if(press("X")){
cur="X";
} else {
cur="Y";
}
}
if(n==1){return cur;}
string valids="";
rep(i, 4){
if(val[i]==cur[0]){continue;}
valids+=val[i];
}
for(int i = 1; i<n-1; i++){
string newCur="";
rep(i, 3){
newCur+=cur+valids[0]+valids[i];
}
newCur+=cur+valids[1];
int coins = press(newCur);
if(coins>=i+2){
cur+=valids[0];
} else if(coins == i+1){
cur+=valids[1];
} else
{
cur+=valids[2];
}
}
rep(i,3){
if(i==2||press(cur+valids[i])==n){cur+=valids[i];break;}
}
return cur;
}
/* signed main(){
int n;
cin >> n;
cout << guess_sequence(n);
} */
