#include <bits/stdc++.h>
using namespace std;
#define name "combo"
#define MAXN 8008
#define pb push_back
#define pf push_front
#define ll long long
#define ii pair<int, int>
#define fs first
#define sc second
#define ill pair<int, ll>
#define lli pair<ll, int>
#define llll pair<ll, ll>
#define all(v) v.begin(),v.end()
#define uni(v) v.erase(unique(all(v)),v.end())
#define bit(n,i) (((n)>>(i))&1)
#define FOR(i,a,b) for (int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for (int i=(a),_b=(b); i>=_b; i--)
#define MASK(i) (1LL<<(i))
const int INF=1e9;
const int MOD=1e9+7;
void add(int &u, int v){
u+=v;
if (u>=MOD) u-=MOD;
}
void sub(int &u, int v){
u-=v;
if (u<0) u+=MOD;
}
void minimize(int &u, int v){
u=min(u,v);
}
void maximize(int &u, int v){
u=max(u,v);
}
long long Rand(long long l, long long r){
ll tmp=0;
FOR(i,1,4) tmp=((tmp<<15)^(((1<<15)-1)&rand()));
return l+tmp%(r-l+1);
}
#include <combo.h>
/*
int kmp[MAXN],match[MAXN];
string st;
int n;
int press(string p){
p=" "+p;
int k=0,res=0;
FOR(i,1,(int)p.size()-1){
while (k>0&&p[i]!=st[k+1]) k=kmp[k];
match[i]=(p[i]==st[k+1]?++k:0);
maximize(res,match[i]);
}
return res;
}
*/
string s[4]={"A","B","X","Y"};
string guess_sequence(int N){
string kq="";
///find 1st letter
string tmp="";
tmp=s[0]+s[1];
int u=-1;
if (press(tmp)>0){
if (press(s[0])>0){
kq+=s[0];
u=0;
}
else{
kq+=s[1];
u=1;
}
}
else{
if (press(s[2])>0){
u=2;
kq+=s[2];
}
else{
u=3;
kq+=s[3];
}
}
swap(s[0],s[u]);
u=0;
///2nd to (N-1)th
FOR(i,2,N-1){
tmp="";
FOR(j,1,3){
tmp+=kq+s[1]+s[j];
}
tmp+=kq+s[2]+s[0];
// cout<<tmp<<" ";
int x=press(tmp);
// cout<<x<<" ";
if (x==i-1+2){
kq+=s[1];
}
else if (x==i-1+1){
kq+=s[2];
}
else{
kq+=s[3];
}
//cout<<kq<<"\n";
}
///Nth
tmp=kq+s[1];
if (press(tmp)==N){
kq+=s[1];
}
else{
tmp=kq+s[2];
if (press(tmp)==N){
kq+=s[2];
}
else kq+=s[3];
}
return kq;
}
/*
int main()
{
cin>>n;
cin>>st;
st=" "+st;
kmp[1]=0;
int k=0;
FOR(i,2,n){
while (k>0&&st[i]!=st[k+1]) k=kmp[k];
kmp[i]=(st[i]==st[k+1]?++k:0);
}
cout<<guess_sequence(n);
return 0;
}
*/
