#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define v(x) vector<x>
#define pb push_back
#define mp make_pair
const ll maxint=2e18;
const ll minint =-2e18;
/*
(͡ ° ͜ʖ ͡ °): Hi, be careful of overflow.
*/
int press(string p);
/*
// comment out when submitting
int press(string p){
cout<<p<<endl;
int x;
cin>>x;
return x;
}
*/
string let[4]={"A","B","X","Y"};
// the first character of S never reappears in it
string guess_sequence(int N){
string res ="";
int cnt = 0;
int avoid = 0;
for(int j=0;j<4;j++){
int x = press((res+let[j]));
if(x == cnt+1){
res+=let[j];
cnt++;
avoid = j;
break;
}
}
for(int i=1;i<N;i++){
for(int j=0;j<4;j++){
if(j != avoid);
int x = press((res+let[j]));
if(x == cnt+1){
res+=let[j];
cnt++;
break;
}
}
}
return res;
}
// comment out when submitting
/*
int main(){
int n;
cin>>n;
cout<<guess_sequence(n)<<'\n';
return 0;
}
*/
