#ifndef LOCALONLY
#include "combo.h"
#endif // LOCALONLY
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; i++)
#define BIT(i, x) (((x) >> (i)) & 1)
#define MK(i) (1LL << (i))
#define all(v) v.begin(), v.end()
#define sz(v) ((int)v.size())
#define F first
#define S second
template <class t> bool maxi(t &x, t const &y)
{
return x < y ? x = y, 1 : 0;
}
template <class t> bool mini(t &x, t const &y)
{
return x > y ? x = y, 1 : 0;
}
#ifdef LOCALONLY
#define name "2742"
string guess_sequence(int);
struct Jury
{
int n;
string s;
int cnt = 0;
int QueryLim;
string moves = "ABXY";
void Input()
{
cin >> n >> s;
QueryLim = 4 * n;
}
bool Check(char ch)
{
for (auto &x : moves) if (ch == x) return true;
return false;
}
int press(string t)
{
assert(++cnt <= QueryLim);
assert(sz(t) <= 4 * n);
for (auto &ch : t) assert(Check(ch));
int res = 0;
int len = 0;
REP(i, sz(t))
{
if (len < n && s[len] == t[i]) len++;
else if (s[0] == t[i]) len = 1;
else len = 0;
maxi(res, len);
}
return res;
}
void Judge()
{
assert(guess_sequence(n) == s);
}
} jury;
int press(string t)
{
return jury.press(t);
}
#endif // LOCALONLY
int n;
string moves = "ABXY";
string guess_sequence(int NN)
{
n = NN;
string s = "";
if (press("AB"))
{
if (press("A")) s = "A";
else s = "B";
}
else if (press("X")) s = "X";
else s = "Y";
string haha = "";
for (auto &ch : moves) if (ch != s[0]) haha += ch;
FOR(i, 1, n - 2)
{
int len = press(s + haha[0] + s + haha[1] + haha[0] + s + haha[1] + haha[1] + s + haha[1] + haha[2]);
if (len == i + 1) s += haha[0];
else if (len == i + 2) s += haha[1];
else s += haha[2];
}
if (n >= 3)
{
if (press(s + haha[0]) == n) s += haha[0];
else if (press(s + haha[1]) == n) s += haha[1];
else s += haha[2];
}
return s;
}
#ifdef LOCALONLY
int main()
{
freopen(name".inp", "r", stdin);
jury.Input();
jury.Judge();
return 0;
}
#endif // LOCALONLY
